CONCLUDING COMMENTARY. ON THE FORM AND DISTRIBUTION OF THE VASCULAR SYSTEM AS A WHOLE. ANOMALIES.—RAMIFICATION.—ANASTOMOSIS.I.—The heart, in all stages of its development, is to the vascular system what the point of a circle is to the circumference—namely, at oncethe beginning and the end.The heart, occupying, it may be said, the centre of the thorax, circulates the blood in the same way, by similar channels, to an equal extent, in equal pace, and at the same period of time, through both sides of the body. In its adult normal condition, the heart presents itself as a double or symmetrical organ. The two hearts, though united and appearing single, are nevertheless, as to their respective cavities, absolutely distinct. Each heart consists again of two compartments—an auricle and a ventricle. The two auricles are similar in structure and form. The two ventricles are similar in the same respects. A septum divides the two auricles, and another—the two ventricles. Between the right auricle and ventricle, forming the right heart, there exists a valvular apparatus (tricuspid), by which these two compartments communicate; and a similar valve (bicuspid) admits of communication between the left auricle and ventricle. The two hearts being distinct, and the main vessels arising from each respectively being distinct likewise, it follows that the capillary peripheries of these vessels form the only channels through which the blood issuing from one heart can enter the other.II.—As the aorta of the left heart ramifies throughout all parts of the body, and as the countless ramifications of this vessel terminate in an equal number of ramifications of the principal veins of the right heart, it will appear that between the systemic vessels of the two hearts respectively, the capillary anastomotic circulation reignsuniversal.III.—The body generally is marked by the median line, from the vertex to the perinaeum, into corresponding halves. All parts excepting the main bloodvessels in the neighbourhood of the heart are naturally divisible by this line into equals. The vessels of each heart, in being distributed to both sides of the body alike, cross each other at the median line, and hence they are inseparable according to this line, unless by section. If the vessels proper to each heart, right and left, ramified alone within the limits of their respective sides of the body, then their capillary anastomosis could only take place along the median line, and here in such case they might be separated by median section into two distinct systems. But as each system is itself double in branching into both sides of the body, the two would be at the same time equally divided by vertical section. From this it will appear that the vessels belonging toeachheart form a symmetrical system, corresponding to the sides of the body, and that the capillary anastomosis of these systemic veins and arteries is divisible intotwo great fields, one situated on either side of the median line, and touching at this line.IV.—The vessels of the right heart do not communicate at their capillary peripheries, for its veins are systemic, and its arteries are pulmonary. The vessels of the left heart do not anastomose, for its veins are pulmonary, and its arteries are systemic. The arteries of the right and left hearts cannot anastomose, for the former are pulmonary, and the latter are systemic; and neither can the veins of the right and left hearts, for a similar reason. Hence, therefore, there can be, between the vessels of both hearts, buttwo provinces of anastomosis—viz., that of the lungs, and that of the system. In the lungs, the arteries of the right heart and the veins of the left anastomose. In the body generally (not excepting the lungs), the arteries of the left heart, and the veins of the right, anastomose; and thus in the pulmonary and the systemic circulation, each heart plays an equal part through the medium of its proper vessels. The pulmonary bear to the systemic vessels the same relation as a lesser circle contained within a greater; and the vessels of each heart form the half of each circle, the arteries of the one being opposite the veins of the other.V.—The two hearts being, by the union of their similar forms, as one organ in regard to place, act, by an agreement of their corresponding functions, as one organ in respect to time. The action of the auricles is synchronous; that of the ventricles is the same; that of the auricles and ventricles is consentaneous; and that of the whole heart is rhythmical, or harmonious—the diastole of the auricles occurring in harmonical time with the systole of the ventricles, andvice versa. By this correlative action of both hearts, the pulmonary and systemic circulations take place synchronously; and the phenomena resulting in both reciprocate and balance each other. In the pulmonary circulation, the blood is aerated, decarbonized, and otherwise depurated; whilst in the systemic circulation, it is carbonized and otherwise deteriorated.VI.—The circulation through the lungs and the system is carried on through vessels having the following form and relative position, which, as being most usual, is accounted normal. The two brachio-cephalic veins joining at the root of the neck, and the two common iliac veins joining in front of the lumbar vertebrae, form the superior and inferior venae cavae, by which the blood is returned from the upper and lower parts of the body to the right auricle, and thence it enters the right ventricle, by which it is impelled through the pulmonary artery into the two lungs; and from these it is returned (aerated) by the pulmonary veins to the left auricle, which passes it into the left ventricle, and by this it is impelled through the systemic aorta, which branches throughout the body in a similar way to the systemic veins, with which the aortic branches anastomose generally. On viewing together the system of vessels proper to each heart, they will be seen to exhibit in respect to the body a figure in doubly symmetrical arrangement, of which the united hearts form a duplex centre. At this centre, which is the theatre of metamorphosis, the principal abnormal conditions of the bloodvessels appear; and in order to find the signification of these, we must retrace the stages of development.VII.—From the first appearance of an individualized centre in the vascular area of the human embryo, that centre (punctum saliens) and the vessels immediately connected with it, undergo a phaseal metamorphosis, till such time after birth as they assume their permanent character. In each stage of metamorphosis, the embryo heart and vessels typify the normal condition of the organ in one of the lower classes of animals. The several species of the organ in these classes are parallel to the various stages of change in the human organ. In its earliest condition, the human heart presents the form of a simple canal, similar to that of the lower Invertebrata, the veins being connected with its posterior end, while from its anterior end a single artery emanates. The canal next assumes a bent shape, and the vessels of both its ends become thereby approximated. The canal now being folded upon itself in heart-shape, next becomes constricted in situations, marking out the future auricle and ventricle and arterial bulb, which still communicate with each other. From the artery are given off on either side symmetrically five branches (branchial arches), which arch laterally from before, outwards and backwards, and unite in front of the vertebrae, forming the future descending aorta. In this condition, the human heart and vessels resemble the Piscean pipe. The next changes which take place consist in the gradual subdivision, by means of septa, of the auricle and ventricle respectively into two cavities. On the separation of the single auricle into two, while the ventricle as yet remains single, the heart presents that condition which is proper to the Reptilian class. The interauricular and interventricular septa, by gradual development from without inwards, at length meet and coalesce, thereby dividing the two cavities into four—two auricles and two ventricles—a condition proper to the Avian and Mammalian classes generally. In the centre of the interauricular septum of the human heart, an aperture (foramen ovale) is left as being necessary to the foetal circulation. While the septa are being completed, the arterial bulb also becomes divided by a partition formed in its interior in such a manner as to adjust the two resulting arteries, the one in connexion with the right, the other with the left ventricle. The right ventricular artery (pulmonary aorta) so formed, has assigned to it the fifth (posterior) opposite pair of arches, and of these the right one remaining pervious to the point where it gives off the right pulmonary branch, becomes obliterated beyond this point to that where it joins the descending aorta, while the left arch remains pervious during foetal life, as theductus arteriosusstill communicating with the descending aorta, and giving off at its middle the left pulmonary branch. The left ventricular artery (systemic aorta) is formed of the fourth arch of the left side, while the opposite arch (fourth right) is altogether obliterated. The third and second arches remain pervious on both sides, afterwards to become the right and left brachio-cephalic arteries. The first pair of arches, if not converted into the vertebral arteries, or the thyroid axes, are altogether metamorphosed. By these changes the heart and primary arteries assume the character in which they usually present themselves at birth, and in all probability the primary veins corresponded in form, number, and distribution with the arterial vessels, and underwent, at the same time, a similar mode of metamorphosis. One point in respect to the original symmetrical character of the primary veins is demonstrable—namely, that in front of the aortic branches the right and left brachio-cephalic veins, after joining by a cross branch, descend separately on either side of the heart, and enter (as two superior venae cavae) the right auricle by distinct orifices. In some of the lower animals, this double condition of the superior veins is constant, but in the human species the left vein below the cross branch (left brachio-cephalic) becomes obliterated, whilst the right vein (vena cava superior) receives the two brachio-cephalic veins, and in this condition remains throughout life. After birth, on the commencement of respiration, theforamen ovaleof the interauricular septum closes, and theductus arteriosusbecomes impervious. This completes the stages of metamorphosis, and changes the course of the simple foetal circulation to one of a more complex order—viz., the systemic-pulmonary characteristic of the normal state in the adult body.VIII.—Such being the phases of metamorphosis of the primary (branchial) arches which yield the vessels in their normal adult condition, we obtain in this history an explanation of the signification not only of such of their anomalies as are on record, but of such also as arepotentialin the law of development; a few of them will suffice to illustrate the meaning of the whole number:—lst, The interventricular as well as the interauricular septum may be arrested in growth, leaving an aperture in the centre of each; the former condition isnatural to the human foetus, the latterto the reptilian class,while both would beabnormal in the human adult. 2nd. The heart may becleft at its apexin the situation of the interventricular septum—a conditionnatural to the Dugong, A similar cleavage may divide thebase of the heartin the situation of the interauricular septum. 3rd. Thepartitioning of the bulbus arteriosusmay occur in such a manner as to assign to the two aortae a relative position, thereverseof that which theynormallyoccupy—thepulmonary aortaspringing from theleft ventricleand thesystemic aortaarising from theright,and giving off from its arch theprimary branchesin the usual order. [Footnote 1] 4th. As thetwo aortaeresult from adivisionof thecommon primary vessel (bulbus arteriosus), anarrestin the growth of the partition would leave them still asone vessel, which (supposing the ventricular septum remained also incomplete) would then arise from asingle ventricle. 5th.Theductus arteriosusmay remainpervious, and while co-existing with the properaortic arch, two archeswould then appear on theleft side. 6th. Thesystemic normal aortic archmay be obliterated as far up as theinnominate branch, and while theductus arteriosusremainspervious,and leading from the pulmonary artery to the descending part of the aortic arch, this vessel would then present the appearance ofa branchascending from the left side and giving off the brachio-cephalic arteries. Theright ventricular arterywould then, through the medium of theductus arteriosus, supply both the lungs and the system. Such a state of the vessels would require (in order that the circulation of a mixed blood might be carried on) that the two ventricles freely communicate. 7th. If thefourth archof theright sideremained pervious opposite theproper aortic arch, there would existtwo aortic archesplacedsymmetrically, one on either side of the vertebral column, and, joining below, wouldinclude in their circlethe trachea and oesophagus. 8th. If thefifth archof theright sideremainedperviousopposite theopen ductus arteriosus, both vessels would present a similar arrangement, astwo symmetrical ducti arteriosico-existing with symmetrical aortic arches. 9th. If the vessels appearedco-existingin thetwo conditionslast mentioned, they would representfour aortic arches, two on either side of the vertebral column.10th. If thefourth right arch, instead of the fourth left(aorta), remainedpervious, thesystemic aortic archwould then be turned to theright sideof the vertebral column, and have the trachea and oesophagus on itsleft. 11th.When thebulbus arteriosusdivides itself intothree parts, thetwo lateral parts, in becoming connected with theleft ventricle, will represent adouble ascending systemic aorta, and having thepulmonary arterypassingbetween themto the lungs. 12th. When of thetwo original superior venae cavaetheright oneinstead of the left suffers metamorphosis, thevena cava superiorwill then appear on theleft sideof thenormal aortic arch.[Footnote 2] Of these malformations, some are rather frequently met with, others very seldom, and others cannot exist compatible with life after birth. Those which involve a more or less imperfect discharge of the blood-aerating functions of the lungs, are in those degrees more or less fatal, and thus nature aborting as to the fitness of her creation, cancels it.[Footnote 1: This physiological truth has, I find, been applied by Dr. R. Quain to the explanation of a numerous class of malformations connected with the origins of the great vessels from the heart, and of their primary branches. SeeThe Lancet, vol. I. 1842.][Footnote 2: For an analysis of the occasional peculiarities of these primary veins in the human subject, see an able and original monograph in thePhilosophical Transactions,Part 1., 1850, entitled, “On the Development of the Great Anterior Veins in Man and Mammalia.” By John Marshall, F.R.C.S., &c. ]IX.—Theportal system of veinspassingtothe liver, and the hepatic veins passingfromthis organ to join the inferior vena cava, exhibit in respect to the median line of the body an example of a-symmetry, since appearing on the right side, they have no counterparts on the left. As the law of symmetry seems to prevail universally in the development of organized beings, forasmuch as every lateral organ or part has its counterpart, while every central organ is double or complete, in having two similar sides, then the portal system, as being an exception to this law, is as a natural note of interrogation questioning the signification of that fact, and in the following observations, it appears to me, the answer may be found. Every artery in the body has its companion vein or veins. The inferior vena cava passes sidelong with the aorta in the abdomen. Every branch of the aorta which ramifies upon the abdominal parietes has its accompanying vein returning either to the vena cava or the vena azygos, and entering either of these vessels at a point on the same level as that at which itself arises. The renal vessels also have this arrangement. But all the other veins of the abdominal viscera, instead of entering the vena cava opposite their corresponding arteries, unite into a single trunk (vena portae), which enters the liver. The special purpose of this destination of the portal system is obvious, but the function of a part gives no explanation of its form or relative position, whether singular or otherwise. On viewing the vessels in presence of the general law of symmetrical development, it occurs to me that theportalandhepatic veins form one continuous system, which taken inthe totality, represents thecompanion veins of the arteries of the abdominal viscera.The liver under this interpretation appears as a glanddeveloped midwayupon these veins, anddismembering theminto a mesh of countless capillary vessels, (a condition necessary for all processes of secretion,) for the special purpose of decarbonizing the blood. In this great function the liver is an organ correlative or compensative to the lungs, whose office is similar. The secretion of the liver (bile) is fluidform; that of the lungs is aeriform. The bile being necessary to the digestive process, the liver has a duct to convey that product of its secretion to the intestines. The trachea is as it were the duct of the lungs. In the liver, then,the portalandhepatic veinsbeing continuousas veins,the two systems, notwithstanding their apparent distinctness, caused by the intervention of the hepatic lobules, may be regarded as theveins corresponding with the arteries of the coeliac axis, and the two mesenteric.The hepatic artery and the hepatic veins evidently donotpair in the sense ofafferentandefferent,with respect to the liver, both these vessels having destinations as different as those of the bronchial artery and the pulmonary veins in the lungs. The bronchial artery is attended by its vein proper, while the vein which corresponds to the hepatic artery joins either the hepatic or portal veins traversing the liver, and in this position escapes notice.[Footnote][Footnote: In instancing these facts, as serving under comparison to explain how the hepatic vessels constitute noradicalexception to the law of symmetry which presides over the development and distribution of the vascular system as a whole, I am led to inquire in what respect (if in any) the liver as an organ forms an exception to this general law either in shape, in function, or in relative position. While seeing that every central organ is single and symmetrical by the union of two absolutely similar sides, and that each lateral pair of organs is double by the disunion of sides so similar to each other in all respects that the description of either side serves for the other opposite, it has long since seemed to me a reasonable inference that, since the liver on the right has no counterpartas a liveron the left, and that, since the spleen on the left has no counterpartas a spleenon the right, so these two organs (the liver and spleen) must themselves correspond to each other, and as such, express their respective significations. Under the belief that every exception (even though it be normal) to a general law or rule, is, like the anomaly itself, alone explicable according to such law, and expressing a fact not more singular or isolated from other parallel facts than is one form from another, or from all others constituting the graduated scale of being, I would, according to the light of this evidence alone, have no hesitation in stating that the liver and spleen, as opposites, represent corresponding organs, even though they appeared at first view more dissimilar than they really are. In support of this analogy of both organs, which is here, so far as I am aware, originally enunciated for anatomical science, I record the following observations:—1st.Between the opposite parts of thesameorganic entity (between the opposite leaves of the same plant, for example), nature manifests no such absolute difference in any case as exists between the leaf of a plant and of a book. 2ndly.When between two opposite parts of thesameorganic form there appears any differential character, this is simply the result of a modification or metamorphosis of one of the two perfectly similar originals or archetypes, but never carried out to such an extreme degree as to annihilate all trace of their analogy. 3rdly.The liver and the spleen are opposite parts; and as such, they are associated by arteries which arise by a single trunk (coeliac axis) from the aorta, and branch right and left, like indices pointing to the relationship between both these organs, in the same manner as the two emulgent arteries point to the opposite renal organs. 4thly. The liver is divided into two lobes, right and left; the left is less than the right; that quantity which is wanting to the left lobe is equal to the quantity of a spleen; and if in idea we add the spleen to the left lobe of the liver, both lobes of this organ become quantitatively equal, and the whole liver symmetrical; hence, as the liverplusthe spleen represents the whole structural quantity, so the liverminusthe spleen signifies that the two organs now dissevered still relate to each other as parts of the same whole. 5thly. The liver, as beingthree-fourthsof the whole, possesses theductwhich emanates at the centre of all glandular bodies. The spleen, as beingone-fourthof the whole, isdevoidof the duct. The liver having the duct, is functional as a gland, while the spleen having no duct, cannot serve any such function. If, in thus indicating the function which the spleen doesnotpossess, there appears no proof positive of the function which itdoes,perhaps the truth is, that as being the ductless portion of the whole original hepatic quantity, it exists as a thing degenerate and functionless, for it seems that the animal economy suffers no loss of function when deprived of it. 6thly.In early foetal life, the left lobe of the livertouchesthe spleen on the left side; but in the process of abdominal development, the two organs become separated from each other right and left. 7thly.In animals devoid of the spleen, the liver appears of asymmetricalshape, both its lobes beingequal; for that quantity which in other animals has become splenic, is in the former still hepatic. 8thly. In cases of transposition of both organs, it is therightlobe of the liver—thatnearest the spleen,now on the right side—which is thesmallerof the two lobes, proving that whichever lobe be in this condition, thespleen,as being opposite to it,represents the minus hepatic quantity. From these, among other facts, I infer that the spleen is the representative of the liver on the left side, and that as such, its signification being manifest, there exists no exception to the law of animal symmetry. “Tam miram uniformitatem in planetarum systemate, necessario fatendum est intelligentia et concilio fuisse effectam. Idemque dici possit de uniformitate illa quae est in corporibus animalium. Habent videlicet animalia pleraque omnia, bina latera, dextrum et sinistrum, forma consimili: et in lateribus illis, a posteriore quidem corporis sui parte, pedes binos; ab anteriori autem parte, binos armos, vel pedes, vel alas, humeris affixos: interque humeros collum, in spinam excurrens, cui affixum est caput; in eoque capite binas aures, binos oculos, nasum, os et linguam; similiter posita omnia, in omnibus fere animalibus.”—Newton, Optices, sive de reflex, &c. p. 411.]X.—The heart, though being itself the recipient, the prime mover, and the dispenser of the blood, does not depend either for its growth, vitality, or stimulus to action, upon the blood under these uses, but upon the blood circulating through vessels which are derived from its main systemic artery, and disposed in capillary ramifications through its substance, in the manner of the nutrient vessels of all other organs. The twocoronary arteriesof the heart arise from the systemic aorta immediately outside the semilunar valves, situated in the root of this vessel, and in passing right and left along the auriculo-ventricular furrows, they send off some branches for the supply of the organ itself, and others by which both vessels anastomose freely around its base and apex. Thevasa cordisform an anastomotic circulation altogether isolated from the vessels of the other thoracic organs, and also from those distributed to the thoracic parietes. The coronary arteries are accompanied by veins which open by distinct orifices (foramina Thebesii) into the right auricle. Like the heart itself, its main vessels do not depend for their support upon the blood conveyed by them, but upon that circulated by the small arteries (vasa vasorum) derived either from the vessel upon which they are distributed, or from some others in the neighbourhood. These little arteries are attended by veins of a corresponding size (venules) which enter the venae comites, thus carrying out the general order of vascular distribution to the minutest particular. Besides the larger nerves which accompany the main vessels, there are delicate filaments of the cerebro-spinal and sympathetic system distributed to their coats, for the purpose, as it is supposed, of governing their “contractile movements.” Thevasa vasorumform an anastomosis as well upon the inner surface of the sheath as upon the artery contained in this part; and hence in the operation for tying the vessel, the rule should be to disturb its connexions as little as possible, otherwise its vitality, which depends upon these minute branches, will, by their rupture,be destroyed in the situation of the ligature, where it is most needed.XI.—The branches of the systemic aortaform frequent anastomoses with each other in all parts of the body.This anastomosis occurs chiefly amongst the branches of the main arteries proper to either side. Those branches of the opposite vessels which join at the median line are generally of very small size. There are but few instances in which a large blood vesselcrosses the central line from its own side to the other. Anastomosis at the median line between opposite vessels happens either by afusion of their sideslying parallel, as for example (and the only one) that of the two vertebral arteries on the basilar process of the occipital bone; or else by a directend-to-end union, of which the lateral pair of cerebral arteries, forming thecircle of Willis, and the two labial arteries, forming the coronary, are examples. The branches of the main arteries of one side form numerous anastomoses in the muscles and in the cellular and adipose tissue generally. Other special branches derived from the parent vessel above and below the several joints ramify and anastomose so very freely over the surfaces of these parts, and seem to pass in reference to them out of their direct course, that to effect this mode of distribution appears to be no less immediate a design than to support the structures of which the joints are composed.XII.—The innominate artery. When this vessel is tied, the free direct circulation through the principal arteries of the right arm, and the right side of the neck, head, and brain, becomes arrested; and the degree of strength of the recurrent circulation depends solely upon the amount of anastomosing points between the following arteries of the opposite sides. The small terminal branches of the two occipital, the two auricular, the two superficial temporal, and the two frontal, inosculate with each other upon the sides, and over the vertex of the head; the two vertebral, and the branches of the internal carotid, at the base and over the surface of the brain; the two facial with each other, and with the frontal above and mental below, at the median line of the face; the two internal maxillary by their palatine, pharyngeal, meningeal, and various other branches upon the surface of the parts to which they are distributed; and lastly, the two superior thyroid arteries inosculate around the larynx and in the thyroid body. By these anastomoses, it will be seen that the circulation is restored to the branches of the common carotid almost solely. In regard to the subclavian artery, the circulation would be carried on through the anastomosing branches of the two inferior thyroid in the thyroid body; of the two vertebral, in the cranium and upon the cervical vertebrae; of the two internal mammary, with each other behind the sternum, and with the thoracic branches of the axillary and the superior intercostal laterally; lastly, through the anastomosis of the ascending cervical with the descending branch of the occipital, and with the small lateral offsets of the vertebral.XIII.—The common carotid arteries,Of these two vessels, the left one arising, in general, from the arch of the aorta, is longer than the right one by the measure of the innominate artery from which the right arises. When either of the common carotids is tied, the circulation will be maintained through the anastomosing branches of the opposite vessels as above specified. When the vertebral or the inferior thyroid branch arises from the middle of the common carotid, this vessel will have an additional source of supply if the ligature be applied to it below the origin of such branch. In the absence of the innominate artery, the right as well as the left carotid will be found to spring directly from the aortic arch.XIV.—The subclavian arteries.When a ligature is applied to the inner third of this vessel within its primary branches, the collateral circulation is carried on by the anastomoses of the arteries above mentioned; but if the vertebral or the inferior thyroid arises either from the aorta or the common carotid, the sources of arterial supply in respect to the arm will, of course, be less numerous. When the outer portion of the subclavian is tied between the scalenus and the clavicle, while the branches arise from its inner part in their usual position and number, the collateral circulation in reference to the arm is maintained by the following anastomosing branches:—viz., those of the superficialis colli, and the supra and posterior scapular, with those of the acromial thoracic; the subscapular, and the anterior and posterior circumflex around the shoulder-joint, and over the dorsal surface of the scapula; and those of the internal mammary and superior intercostal, with those of the thoracic arteries arising from the axillary. Whatever be the variety as to their mode or place of origin, the branches emanating from the subclavian artery are constant as to their destination. The length of the inner portion of the right subclavian will vary according to the place at which it arises, whether from the innominate artery, from the ascending, or from the descending part of the aortic arch.XV.—The axillary artery. As this vessel gives off throughout its whole length, numerous branches which inosculate principally with the scapular, mammary, and superior intercostal branches of the subclavian, it will be evident that, in tying it above its own branches, the anastomotic circulation will with much greater freedom be maintained in respect to the arm, than if the ligature be applied below those branches. Hence, therefore, when the axillary artery is affected with aneurism, thereby rendering it unsafe to apply a ligature to this vessel, it becomes not only pathologically, but anatomically, the more prudent measure to tie the subclavian immediately above the clavicle.XVI.—The brachial artery, When this artery is tied immediately below the axilla, the collateral circulation will be weakly maintained, in consequence of the small number of anastomosing branches arising from it above and below the seat of the ligature. The two circumflex humeri alone send down branches to inosculate with the small muscular offsets from the middle of the brachial artery. When tied in the middle of the arm between the origins of the superior and inferior profunda arteries, the collateral circulation will depend chiefly upon the anastomosis of the former vessel with the recurrent branch of the radial, and of muscular branches with each other. When the ligature is applied to the lower third of the vessel, the collateral circulation will be comparatively free through the anastomoses of the two profundi and anastomotic branches with the radial, interosseous, and ulnar recurrent branches. If the artery happen to divide in the upper part of the arm into either of the branches of the forearm, or into all three, a ligature applied to any one of them will, of course, be insufficient to arrest the direct circulation through the forearm, if this be the object in view.XVII.—Theradial artery.If this vessel be tied in any part of its course, the collateral circulation will depend principally upon the free communications between it and the ulnar, through the medium of the superficial and deep palmar arches and those of the branches derived from both vessels, and from the two interossei distributed to the fingers and back of the hand.XVIII.—Theulnar artery.When this vessel is tied, the collateral circulation will depend upon the anastomosis of the palmar arches, as in the case last mentioned. While the radial, ulnar, and interosseous arteries spring from the same main vessel, and are continuous with each other in the hand, they represent the condition of a circle of which, when either side is tied, the blood will pass in a current of almost equal strength towards the seat of the ligature from above and below—a circumstance which renders it necessary to tie both ends of the vessel in cases of wounds.XIX.—Thecommon iliac artery. When a ligature is applied to the middle of this artery, the direct circulation becomes arrested in the lower limb and side of the pelvis corresponding to the vessel operated on. The collateral circulation will then be carried on by the anastomosis of the following branches—viz., those of the lumbar, the internal mammary, and the epigastric arteries of that side with each other, and with their fellows in the anterior abdominal parietes; those of the middle and lateral sacral; those of the superior with the middle and inferior haemorrhoidal; those of the aortic and internal iliac uterine branches in the female; and of the aortic and external iliac spermatic branches in the male. The anastomoses of these arteries with their opposite fellows along the median line, are much less frequent than those of the arteries of the neck and head.XX.—The external iliac artery.This vessel, when tied at its middle, will have its collateral circulation carried on by the anastomoses of the internal mammary with the epigastric; by those of the ilio-lumbar with the circumflex ilii; those of the internal circumflex femoris, and superior perforating arteries of the profunda femoris, with the obturator, when this branch arises from the internal iliac; those of the gluteal with the external circumflex; those of the latter with the sciatic; and those of both obturators, with each other, when arising—the one from the internal, the other from the external iliac. Not unfrequently either the epigastric, obturator, ilio-lumbar, or circumflex ilii, arises from the middle of the external iliac, in which case the ligature should be placed above such branch.XXI.—Thecommon femoral artery. On considering the circles of inosculation formed around the innominate bone between the branches derived from the iliac arteries near the sacro-iliac junction, and those emanating from the common femoral, above and below Poupart’s ligament, it will at once appear that, in respect to the lower limb, the collateral circulation will occur more freely if the ligature be applied to the main vessel (external iliac) than if to the common femoral below its branches.XXII.—Thesuperficial femoral artery. When a ligature is applied to this vessel at the situation where it is overlapped by the sartorius muscle, the collateral circulation will be maintained by the following arteries:—the long descending branches of the external circumflex beneath the rectus muscle, inosculate with the muscular branches of the anastomotica magna springing from the lower third of the main vessel; the three perforating branches of the profunda inosculate with the latter vessel, with the sciatic, and with the articular and muscular branches around the knee-joint.XXIII.—Thepopliteal artery.When any circumstance renders it necessary to tie this vessel in preference to the femoral, the ligature should be placed above its upper pair of articular branches; for by so doing a freer collateral circulation will take place in reference to the leg. The ligature in this situation will lie between the anastomotic and articular arteries, which freely communicate with each other.XXIV.—Theanterior and posterior tibial and peronoeal arteries.As these vessels correspond to the arteries of the forearm, the observations which apply to the one set apply also to the other. [Footnote][Footnote: For a complete history of the general vascular system, seeThe Anatomy of the Arteries of the Human Body, by Richard Quain, F.R.S., &c., in which work, besides the results of the author’s own great experience and original observations, will be found those of Haller’s, Scarpa’s, Tiedemann’s, &c., systematically arranged with a view to operative surgery.]THE END.
I.—The heart, in all stages of its development, is to the vascular system what the point of a circle is to the circumference—namely, at oncethe beginning and the end.The heart, occupying, it may be said, the centre of the thorax, circulates the blood in the same way, by similar channels, to an equal extent, in equal pace, and at the same period of time, through both sides of the body. In its adult normal condition, the heart presents itself as a double or symmetrical organ. The two hearts, though united and appearing single, are nevertheless, as to their respective cavities, absolutely distinct. Each heart consists again of two compartments—an auricle and a ventricle. The two auricles are similar in structure and form. The two ventricles are similar in the same respects. A septum divides the two auricles, and another—the two ventricles. Between the right auricle and ventricle, forming the right heart, there exists a valvular apparatus (tricuspid), by which these two compartments communicate; and a similar valve (bicuspid) admits of communication between the left auricle and ventricle. The two hearts being distinct, and the main vessels arising from each respectively being distinct likewise, it follows that the capillary peripheries of these vessels form the only channels through which the blood issuing from one heart can enter the other.
II.—As the aorta of the left heart ramifies throughout all parts of the body, and as the countless ramifications of this vessel terminate in an equal number of ramifications of the principal veins of the right heart, it will appear that between the systemic vessels of the two hearts respectively, the capillary anastomotic circulation reignsuniversal.
III.—The body generally is marked by the median line, from the vertex to the perinaeum, into corresponding halves. All parts excepting the main bloodvessels in the neighbourhood of the heart are naturally divisible by this line into equals. The vessels of each heart, in being distributed to both sides of the body alike, cross each other at the median line, and hence they are inseparable according to this line, unless by section. If the vessels proper to each heart, right and left, ramified alone within the limits of their respective sides of the body, then their capillary anastomosis could only take place along the median line, and here in such case they might be separated by median section into two distinct systems. But as each system is itself double in branching into both sides of the body, the two would be at the same time equally divided by vertical section. From this it will appear that the vessels belonging toeachheart form a symmetrical system, corresponding to the sides of the body, and that the capillary anastomosis of these systemic veins and arteries is divisible intotwo great fields, one situated on either side of the median line, and touching at this line.
IV.—The vessels of the right heart do not communicate at their capillary peripheries, for its veins are systemic, and its arteries are pulmonary. The vessels of the left heart do not anastomose, for its veins are pulmonary, and its arteries are systemic. The arteries of the right and left hearts cannot anastomose, for the former are pulmonary, and the latter are systemic; and neither can the veins of the right and left hearts, for a similar reason. Hence, therefore, there can be, between the vessels of both hearts, buttwo provinces of anastomosis—viz., that of the lungs, and that of the system. In the lungs, the arteries of the right heart and the veins of the left anastomose. In the body generally (not excepting the lungs), the arteries of the left heart, and the veins of the right, anastomose; and thus in the pulmonary and the systemic circulation, each heart plays an equal part through the medium of its proper vessels. The pulmonary bear to the systemic vessels the same relation as a lesser circle contained within a greater; and the vessels of each heart form the half of each circle, the arteries of the one being opposite the veins of the other.
V.—The two hearts being, by the union of their similar forms, as one organ in regard to place, act, by an agreement of their corresponding functions, as one organ in respect to time. The action of the auricles is synchronous; that of the ventricles is the same; that of the auricles and ventricles is consentaneous; and that of the whole heart is rhythmical, or harmonious—the diastole of the auricles occurring in harmonical time with the systole of the ventricles, andvice versa. By this correlative action of both hearts, the pulmonary and systemic circulations take place synchronously; and the phenomena resulting in both reciprocate and balance each other. In the pulmonary circulation, the blood is aerated, decarbonized, and otherwise depurated; whilst in the systemic circulation, it is carbonized and otherwise deteriorated.
VI.—The circulation through the lungs and the system is carried on through vessels having the following form and relative position, which, as being most usual, is accounted normal. The two brachio-cephalic veins joining at the root of the neck, and the two common iliac veins joining in front of the lumbar vertebrae, form the superior and inferior venae cavae, by which the blood is returned from the upper and lower parts of the body to the right auricle, and thence it enters the right ventricle, by which it is impelled through the pulmonary artery into the two lungs; and from these it is returned (aerated) by the pulmonary veins to the left auricle, which passes it into the left ventricle, and by this it is impelled through the systemic aorta, which branches throughout the body in a similar way to the systemic veins, with which the aortic branches anastomose generally. On viewing together the system of vessels proper to each heart, they will be seen to exhibit in respect to the body a figure in doubly symmetrical arrangement, of which the united hearts form a duplex centre. At this centre, which is the theatre of metamorphosis, the principal abnormal conditions of the bloodvessels appear; and in order to find the signification of these, we must retrace the stages of development.
VII.—From the first appearance of an individualized centre in the vascular area of the human embryo, that centre (punctum saliens) and the vessels immediately connected with it, undergo a phaseal metamorphosis, till such time after birth as they assume their permanent character. In each stage of metamorphosis, the embryo heart and vessels typify the normal condition of the organ in one of the lower classes of animals. The several species of the organ in these classes are parallel to the various stages of change in the human organ. In its earliest condition, the human heart presents the form of a simple canal, similar to that of the lower Invertebrata, the veins being connected with its posterior end, while from its anterior end a single artery emanates. The canal next assumes a bent shape, and the vessels of both its ends become thereby approximated. The canal now being folded upon itself in heart-shape, next becomes constricted in situations, marking out the future auricle and ventricle and arterial bulb, which still communicate with each other. From the artery are given off on either side symmetrically five branches (branchial arches), which arch laterally from before, outwards and backwards, and unite in front of the vertebrae, forming the future descending aorta. In this condition, the human heart and vessels resemble the Piscean pipe. The next changes which take place consist in the gradual subdivision, by means of septa, of the auricle and ventricle respectively into two cavities. On the separation of the single auricle into two, while the ventricle as yet remains single, the heart presents that condition which is proper to the Reptilian class. The interauricular and interventricular septa, by gradual development from without inwards, at length meet and coalesce, thereby dividing the two cavities into four—two auricles and two ventricles—a condition proper to the Avian and Mammalian classes generally. In the centre of the interauricular septum of the human heart, an aperture (foramen ovale) is left as being necessary to the foetal circulation. While the septa are being completed, the arterial bulb also becomes divided by a partition formed in its interior in such a manner as to adjust the two resulting arteries, the one in connexion with the right, the other with the left ventricle. The right ventricular artery (pulmonary aorta) so formed, has assigned to it the fifth (posterior) opposite pair of arches, and of these the right one remaining pervious to the point where it gives off the right pulmonary branch, becomes obliterated beyond this point to that where it joins the descending aorta, while the left arch remains pervious during foetal life, as theductus arteriosusstill communicating with the descending aorta, and giving off at its middle the left pulmonary branch. The left ventricular artery (systemic aorta) is formed of the fourth arch of the left side, while the opposite arch (fourth right) is altogether obliterated. The third and second arches remain pervious on both sides, afterwards to become the right and left brachio-cephalic arteries. The first pair of arches, if not converted into the vertebral arteries, or the thyroid axes, are altogether metamorphosed. By these changes the heart and primary arteries assume the character in which they usually present themselves at birth, and in all probability the primary veins corresponded in form, number, and distribution with the arterial vessels, and underwent, at the same time, a similar mode of metamorphosis. One point in respect to the original symmetrical character of the primary veins is demonstrable—namely, that in front of the aortic branches the right and left brachio-cephalic veins, after joining by a cross branch, descend separately on either side of the heart, and enter (as two superior venae cavae) the right auricle by distinct orifices. In some of the lower animals, this double condition of the superior veins is constant, but in the human species the left vein below the cross branch (left brachio-cephalic) becomes obliterated, whilst the right vein (vena cava superior) receives the two brachio-cephalic veins, and in this condition remains throughout life. After birth, on the commencement of respiration, theforamen ovaleof the interauricular septum closes, and theductus arteriosusbecomes impervious. This completes the stages of metamorphosis, and changes the course of the simple foetal circulation to one of a more complex order—viz., the systemic-pulmonary characteristic of the normal state in the adult body.
VIII.—Such being the phases of metamorphosis of the primary (branchial) arches which yield the vessels in their normal adult condition, we obtain in this history an explanation of the signification not only of such of their anomalies as are on record, but of such also as arepotentialin the law of development; a few of them will suffice to illustrate the meaning of the whole number:—lst, The interventricular as well as the interauricular septum may be arrested in growth, leaving an aperture in the centre of each; the former condition isnatural to the human foetus, the latterto the reptilian class,while both would beabnormal in the human adult. 2nd. The heart may becleft at its apexin the situation of the interventricular septum—a conditionnatural to the Dugong, A similar cleavage may divide thebase of the heartin the situation of the interauricular septum. 3rd. Thepartitioning of the bulbus arteriosusmay occur in such a manner as to assign to the two aortae a relative position, thereverseof that which theynormallyoccupy—thepulmonary aortaspringing from theleft ventricleand thesystemic aortaarising from theright,and giving off from its arch theprimary branchesin the usual order. [Footnote 1] 4th. As thetwo aortaeresult from adivisionof thecommon primary vessel (bulbus arteriosus), anarrestin the growth of the partition would leave them still asone vessel, which (supposing the ventricular septum remained also incomplete) would then arise from asingle ventricle. 5th.Theductus arteriosusmay remainpervious, and while co-existing with the properaortic arch, two archeswould then appear on theleft side. 6th. Thesystemic normal aortic archmay be obliterated as far up as theinnominate branch, and while theductus arteriosusremainspervious,and leading from the pulmonary artery to the descending part of the aortic arch, this vessel would then present the appearance ofa branchascending from the left side and giving off the brachio-cephalic arteries. Theright ventricular arterywould then, through the medium of theductus arteriosus, supply both the lungs and the system. Such a state of the vessels would require (in order that the circulation of a mixed blood might be carried on) that the two ventricles freely communicate. 7th. If thefourth archof theright sideremained pervious opposite theproper aortic arch, there would existtwo aortic archesplacedsymmetrically, one on either side of the vertebral column, and, joining below, wouldinclude in their circlethe trachea and oesophagus. 8th. If thefifth archof theright sideremainedperviousopposite theopen ductus arteriosus, both vessels would present a similar arrangement, astwo symmetrical ducti arteriosico-existing with symmetrical aortic arches. 9th. If the vessels appearedco-existingin thetwo conditionslast mentioned, they would representfour aortic arches, two on either side of the vertebral column.10th. If thefourth right arch, instead of the fourth left(aorta), remainedpervious, thesystemic aortic archwould then be turned to theright sideof the vertebral column, and have the trachea and oesophagus on itsleft. 11th.When thebulbus arteriosusdivides itself intothree parts, thetwo lateral parts, in becoming connected with theleft ventricle, will represent adouble ascending systemic aorta, and having thepulmonary arterypassingbetween themto the lungs. 12th. When of thetwo original superior venae cavaetheright oneinstead of the left suffers metamorphosis, thevena cava superiorwill then appear on theleft sideof thenormal aortic arch.[Footnote 2] Of these malformations, some are rather frequently met with, others very seldom, and others cannot exist compatible with life after birth. Those which involve a more or less imperfect discharge of the blood-aerating functions of the lungs, are in those degrees more or less fatal, and thus nature aborting as to the fitness of her creation, cancels it.
[Footnote 1: This physiological truth has, I find, been applied by Dr. R. Quain to the explanation of a numerous class of malformations connected with the origins of the great vessels from the heart, and of their primary branches. SeeThe Lancet, vol. I. 1842.]
[Footnote 2: For an analysis of the occasional peculiarities of these primary veins in the human subject, see an able and original monograph in thePhilosophical Transactions,Part 1., 1850, entitled, “On the Development of the Great Anterior Veins in Man and Mammalia.” By John Marshall, F.R.C.S., &c. ]
IX.—Theportal system of veinspassingtothe liver, and the hepatic veins passingfromthis organ to join the inferior vena cava, exhibit in respect to the median line of the body an example of a-symmetry, since appearing on the right side, they have no counterparts on the left. As the law of symmetry seems to prevail universally in the development of organized beings, forasmuch as every lateral organ or part has its counterpart, while every central organ is double or complete, in having two similar sides, then the portal system, as being an exception to this law, is as a natural note of interrogation questioning the signification of that fact, and in the following observations, it appears to me, the answer may be found. Every artery in the body has its companion vein or veins. The inferior vena cava passes sidelong with the aorta in the abdomen. Every branch of the aorta which ramifies upon the abdominal parietes has its accompanying vein returning either to the vena cava or the vena azygos, and entering either of these vessels at a point on the same level as that at which itself arises. The renal vessels also have this arrangement. But all the other veins of the abdominal viscera, instead of entering the vena cava opposite their corresponding arteries, unite into a single trunk (vena portae), which enters the liver. The special purpose of this destination of the portal system is obvious, but the function of a part gives no explanation of its form or relative position, whether singular or otherwise. On viewing the vessels in presence of the general law of symmetrical development, it occurs to me that theportalandhepatic veins form one continuous system, which taken inthe totality, represents thecompanion veins of the arteries of the abdominal viscera.The liver under this interpretation appears as a glanddeveloped midwayupon these veins, anddismembering theminto a mesh of countless capillary vessels, (a condition necessary for all processes of secretion,) for the special purpose of decarbonizing the blood. In this great function the liver is an organ correlative or compensative to the lungs, whose office is similar. The secretion of the liver (bile) is fluidform; that of the lungs is aeriform. The bile being necessary to the digestive process, the liver has a duct to convey that product of its secretion to the intestines. The trachea is as it were the duct of the lungs. In the liver, then,the portalandhepatic veinsbeing continuousas veins,the two systems, notwithstanding their apparent distinctness, caused by the intervention of the hepatic lobules, may be regarded as theveins corresponding with the arteries of the coeliac axis, and the two mesenteric.The hepatic artery and the hepatic veins evidently donotpair in the sense ofafferentandefferent,with respect to the liver, both these vessels having destinations as different as those of the bronchial artery and the pulmonary veins in the lungs. The bronchial artery is attended by its vein proper, while the vein which corresponds to the hepatic artery joins either the hepatic or portal veins traversing the liver, and in this position escapes notice.[Footnote]
[Footnote: In instancing these facts, as serving under comparison to explain how the hepatic vessels constitute noradicalexception to the law of symmetry which presides over the development and distribution of the vascular system as a whole, I am led to inquire in what respect (if in any) the liver as an organ forms an exception to this general law either in shape, in function, or in relative position. While seeing that every central organ is single and symmetrical by the union of two absolutely similar sides, and that each lateral pair of organs is double by the disunion of sides so similar to each other in all respects that the description of either side serves for the other opposite, it has long since seemed to me a reasonable inference that, since the liver on the right has no counterpartas a liveron the left, and that, since the spleen on the left has no counterpartas a spleenon the right, so these two organs (the liver and spleen) must themselves correspond to each other, and as such, express their respective significations. Under the belief that every exception (even though it be normal) to a general law or rule, is, like the anomaly itself, alone explicable according to such law, and expressing a fact not more singular or isolated from other parallel facts than is one form from another, or from all others constituting the graduated scale of being, I would, according to the light of this evidence alone, have no hesitation in stating that the liver and spleen, as opposites, represent corresponding organs, even though they appeared at first view more dissimilar than they really are. In support of this analogy of both organs, which is here, so far as I am aware, originally enunciated for anatomical science, I record the following observations:—1st.Between the opposite parts of thesameorganic entity (between the opposite leaves of the same plant, for example), nature manifests no such absolute difference in any case as exists between the leaf of a plant and of a book. 2ndly.When between two opposite parts of thesameorganic form there appears any differential character, this is simply the result of a modification or metamorphosis of one of the two perfectly similar originals or archetypes, but never carried out to such an extreme degree as to annihilate all trace of their analogy. 3rdly.The liver and the spleen are opposite parts; and as such, they are associated by arteries which arise by a single trunk (coeliac axis) from the aorta, and branch right and left, like indices pointing to the relationship between both these organs, in the same manner as the two emulgent arteries point to the opposite renal organs. 4thly. The liver is divided into two lobes, right and left; the left is less than the right; that quantity which is wanting to the left lobe is equal to the quantity of a spleen; and if in idea we add the spleen to the left lobe of the liver, both lobes of this organ become quantitatively equal, and the whole liver symmetrical; hence, as the liverplusthe spleen represents the whole structural quantity, so the liverminusthe spleen signifies that the two organs now dissevered still relate to each other as parts of the same whole. 5thly. The liver, as beingthree-fourthsof the whole, possesses theductwhich emanates at the centre of all glandular bodies. The spleen, as beingone-fourthof the whole, isdevoidof the duct. The liver having the duct, is functional as a gland, while the spleen having no duct, cannot serve any such function. If, in thus indicating the function which the spleen doesnotpossess, there appears no proof positive of the function which itdoes,perhaps the truth is, that as being the ductless portion of the whole original hepatic quantity, it exists as a thing degenerate and functionless, for it seems that the animal economy suffers no loss of function when deprived of it. 6thly.In early foetal life, the left lobe of the livertouchesthe spleen on the left side; but in the process of abdominal development, the two organs become separated from each other right and left. 7thly.In animals devoid of the spleen, the liver appears of asymmetricalshape, both its lobes beingequal; for that quantity which in other animals has become splenic, is in the former still hepatic. 8thly. In cases of transposition of both organs, it is therightlobe of the liver—thatnearest the spleen,now on the right side—which is thesmallerof the two lobes, proving that whichever lobe be in this condition, thespleen,as being opposite to it,represents the minus hepatic quantity. From these, among other facts, I infer that the spleen is the representative of the liver on the left side, and that as such, its signification being manifest, there exists no exception to the law of animal symmetry. “Tam miram uniformitatem in planetarum systemate, necessario fatendum est intelligentia et concilio fuisse effectam. Idemque dici possit de uniformitate illa quae est in corporibus animalium. Habent videlicet animalia pleraque omnia, bina latera, dextrum et sinistrum, forma consimili: et in lateribus illis, a posteriore quidem corporis sui parte, pedes binos; ab anteriori autem parte, binos armos, vel pedes, vel alas, humeris affixos: interque humeros collum, in spinam excurrens, cui affixum est caput; in eoque capite binas aures, binos oculos, nasum, os et linguam; similiter posita omnia, in omnibus fere animalibus.”—Newton, Optices, sive de reflex, &c. p. 411.]
X.—The heart, though being itself the recipient, the prime mover, and the dispenser of the blood, does not depend either for its growth, vitality, or stimulus to action, upon the blood under these uses, but upon the blood circulating through vessels which are derived from its main systemic artery, and disposed in capillary ramifications through its substance, in the manner of the nutrient vessels of all other organs. The twocoronary arteriesof the heart arise from the systemic aorta immediately outside the semilunar valves, situated in the root of this vessel, and in passing right and left along the auriculo-ventricular furrows, they send off some branches for the supply of the organ itself, and others by which both vessels anastomose freely around its base and apex. Thevasa cordisform an anastomotic circulation altogether isolated from the vessels of the other thoracic organs, and also from those distributed to the thoracic parietes. The coronary arteries are accompanied by veins which open by distinct orifices (foramina Thebesii) into the right auricle. Like the heart itself, its main vessels do not depend for their support upon the blood conveyed by them, but upon that circulated by the small arteries (vasa vasorum) derived either from the vessel upon which they are distributed, or from some others in the neighbourhood. These little arteries are attended by veins of a corresponding size (venules) which enter the venae comites, thus carrying out the general order of vascular distribution to the minutest particular. Besides the larger nerves which accompany the main vessels, there are delicate filaments of the cerebro-spinal and sympathetic system distributed to their coats, for the purpose, as it is supposed, of governing their “contractile movements.” Thevasa vasorumform an anastomosis as well upon the inner surface of the sheath as upon the artery contained in this part; and hence in the operation for tying the vessel, the rule should be to disturb its connexions as little as possible, otherwise its vitality, which depends upon these minute branches, will, by their rupture,be destroyed in the situation of the ligature, where it is most needed.
XI.—The branches of the systemic aortaform frequent anastomoses with each other in all parts of the body.This anastomosis occurs chiefly amongst the branches of the main arteries proper to either side. Those branches of the opposite vessels which join at the median line are generally of very small size. There are but few instances in which a large blood vesselcrosses the central line from its own side to the other. Anastomosis at the median line between opposite vessels happens either by afusion of their sideslying parallel, as for example (and the only one) that of the two vertebral arteries on the basilar process of the occipital bone; or else by a directend-to-end union, of which the lateral pair of cerebral arteries, forming thecircle of Willis, and the two labial arteries, forming the coronary, are examples. The branches of the main arteries of one side form numerous anastomoses in the muscles and in the cellular and adipose tissue generally. Other special branches derived from the parent vessel above and below the several joints ramify and anastomose so very freely over the surfaces of these parts, and seem to pass in reference to them out of their direct course, that to effect this mode of distribution appears to be no less immediate a design than to support the structures of which the joints are composed.
XII.—The innominate artery. When this vessel is tied, the free direct circulation through the principal arteries of the right arm, and the right side of the neck, head, and brain, becomes arrested; and the degree of strength of the recurrent circulation depends solely upon the amount of anastomosing points between the following arteries of the opposite sides. The small terminal branches of the two occipital, the two auricular, the two superficial temporal, and the two frontal, inosculate with each other upon the sides, and over the vertex of the head; the two vertebral, and the branches of the internal carotid, at the base and over the surface of the brain; the two facial with each other, and with the frontal above and mental below, at the median line of the face; the two internal maxillary by their palatine, pharyngeal, meningeal, and various other branches upon the surface of the parts to which they are distributed; and lastly, the two superior thyroid arteries inosculate around the larynx and in the thyroid body. By these anastomoses, it will be seen that the circulation is restored to the branches of the common carotid almost solely. In regard to the subclavian artery, the circulation would be carried on through the anastomosing branches of the two inferior thyroid in the thyroid body; of the two vertebral, in the cranium and upon the cervical vertebrae; of the two internal mammary, with each other behind the sternum, and with the thoracic branches of the axillary and the superior intercostal laterally; lastly, through the anastomosis of the ascending cervical with the descending branch of the occipital, and with the small lateral offsets of the vertebral.
XIII.—The common carotid arteries,Of these two vessels, the left one arising, in general, from the arch of the aorta, is longer than the right one by the measure of the innominate artery from which the right arises. When either of the common carotids is tied, the circulation will be maintained through the anastomosing branches of the opposite vessels as above specified. When the vertebral or the inferior thyroid branch arises from the middle of the common carotid, this vessel will have an additional source of supply if the ligature be applied to it below the origin of such branch. In the absence of the innominate artery, the right as well as the left carotid will be found to spring directly from the aortic arch.
XIV.—The subclavian arteries.When a ligature is applied to the inner third of this vessel within its primary branches, the collateral circulation is carried on by the anastomoses of the arteries above mentioned; but if the vertebral or the inferior thyroid arises either from the aorta or the common carotid, the sources of arterial supply in respect to the arm will, of course, be less numerous. When the outer portion of the subclavian is tied between the scalenus and the clavicle, while the branches arise from its inner part in their usual position and number, the collateral circulation in reference to the arm is maintained by the following anastomosing branches:—viz., those of the superficialis colli, and the supra and posterior scapular, with those of the acromial thoracic; the subscapular, and the anterior and posterior circumflex around the shoulder-joint, and over the dorsal surface of the scapula; and those of the internal mammary and superior intercostal, with those of the thoracic arteries arising from the axillary. Whatever be the variety as to their mode or place of origin, the branches emanating from the subclavian artery are constant as to their destination. The length of the inner portion of the right subclavian will vary according to the place at which it arises, whether from the innominate artery, from the ascending, or from the descending part of the aortic arch.
XV.—The axillary artery. As this vessel gives off throughout its whole length, numerous branches which inosculate principally with the scapular, mammary, and superior intercostal branches of the subclavian, it will be evident that, in tying it above its own branches, the anastomotic circulation will with much greater freedom be maintained in respect to the arm, than if the ligature be applied below those branches. Hence, therefore, when the axillary artery is affected with aneurism, thereby rendering it unsafe to apply a ligature to this vessel, it becomes not only pathologically, but anatomically, the more prudent measure to tie the subclavian immediately above the clavicle.
XVI.—The brachial artery, When this artery is tied immediately below the axilla, the collateral circulation will be weakly maintained, in consequence of the small number of anastomosing branches arising from it above and below the seat of the ligature. The two circumflex humeri alone send down branches to inosculate with the small muscular offsets from the middle of the brachial artery. When tied in the middle of the arm between the origins of the superior and inferior profunda arteries, the collateral circulation will depend chiefly upon the anastomosis of the former vessel with the recurrent branch of the radial, and of muscular branches with each other. When the ligature is applied to the lower third of the vessel, the collateral circulation will be comparatively free through the anastomoses of the two profundi and anastomotic branches with the radial, interosseous, and ulnar recurrent branches. If the artery happen to divide in the upper part of the arm into either of the branches of the forearm, or into all three, a ligature applied to any one of them will, of course, be insufficient to arrest the direct circulation through the forearm, if this be the object in view.
XVII.—Theradial artery.If this vessel be tied in any part of its course, the collateral circulation will depend principally upon the free communications between it and the ulnar, through the medium of the superficial and deep palmar arches and those of the branches derived from both vessels, and from the two interossei distributed to the fingers and back of the hand.
XVIII.—Theulnar artery.When this vessel is tied, the collateral circulation will depend upon the anastomosis of the palmar arches, as in the case last mentioned. While the radial, ulnar, and interosseous arteries spring from the same main vessel, and are continuous with each other in the hand, they represent the condition of a circle of which, when either side is tied, the blood will pass in a current of almost equal strength towards the seat of the ligature from above and below—a circumstance which renders it necessary to tie both ends of the vessel in cases of wounds.
XIX.—Thecommon iliac artery. When a ligature is applied to the middle of this artery, the direct circulation becomes arrested in the lower limb and side of the pelvis corresponding to the vessel operated on. The collateral circulation will then be carried on by the anastomosis of the following branches—viz., those of the lumbar, the internal mammary, and the epigastric arteries of that side with each other, and with their fellows in the anterior abdominal parietes; those of the middle and lateral sacral; those of the superior with the middle and inferior haemorrhoidal; those of the aortic and internal iliac uterine branches in the female; and of the aortic and external iliac spermatic branches in the male. The anastomoses of these arteries with their opposite fellows along the median line, are much less frequent than those of the arteries of the neck and head.
XX.—The external iliac artery.This vessel, when tied at its middle, will have its collateral circulation carried on by the anastomoses of the internal mammary with the epigastric; by those of the ilio-lumbar with the circumflex ilii; those of the internal circumflex femoris, and superior perforating arteries of the profunda femoris, with the obturator, when this branch arises from the internal iliac; those of the gluteal with the external circumflex; those of the latter with the sciatic; and those of both obturators, with each other, when arising—the one from the internal, the other from the external iliac. Not unfrequently either the epigastric, obturator, ilio-lumbar, or circumflex ilii, arises from the middle of the external iliac, in which case the ligature should be placed above such branch.
XXI.—Thecommon femoral artery. On considering the circles of inosculation formed around the innominate bone between the branches derived from the iliac arteries near the sacro-iliac junction, and those emanating from the common femoral, above and below Poupart’s ligament, it will at once appear that, in respect to the lower limb, the collateral circulation will occur more freely if the ligature be applied to the main vessel (external iliac) than if to the common femoral below its branches.
XXII.—Thesuperficial femoral artery. When a ligature is applied to this vessel at the situation where it is overlapped by the sartorius muscle, the collateral circulation will be maintained by the following arteries:—the long descending branches of the external circumflex beneath the rectus muscle, inosculate with the muscular branches of the anastomotica magna springing from the lower third of the main vessel; the three perforating branches of the profunda inosculate with the latter vessel, with the sciatic, and with the articular and muscular branches around the knee-joint.
XXIII.—Thepopliteal artery.When any circumstance renders it necessary to tie this vessel in preference to the femoral, the ligature should be placed above its upper pair of articular branches; for by so doing a freer collateral circulation will take place in reference to the leg. The ligature in this situation will lie between the anastomotic and articular arteries, which freely communicate with each other.
XXIV.—Theanterior and posterior tibial and peronoeal arteries.As these vessels correspond to the arteries of the forearm, the observations which apply to the one set apply also to the other. [Footnote]
[Footnote: For a complete history of the general vascular system, seeThe Anatomy of the Arteries of the Human Body, by Richard Quain, F.R.S., &c., in which work, besides the results of the author’s own great experience and original observations, will be found those of Haller’s, Scarpa’s, Tiedemann’s, &c., systematically arranged with a view to operative surgery.]
THE END.