Section of a hen’s eggwithin the ovary.aThe granulary membrane formingthe periphery of the yelk.bVesicleof Purkinje imbedded in the cumulus.cVitellary membrane.dInner andouter layers of the capsule of theovum.eIndusium of the ovary.
The egg is known to consist of two distinct parts, the vitellus or yelk surrounded by its albumen or white; to the former ofthese we now more particularly refer. The yelk is a granular albuminous fluid, contained in a granular membranous sac (theblastodermic membrane) which is covered by an investing membrane called thevitelline membraneoryelk-bag. The impregnated vitellus is retained in its capsule in the ovary, precisely as the ovum of the mammifera is in the Graafian vesicle. The whole ovary in this case has a clustered appearance, like a bunch of grapes, each capsule being suspended by a short pedicle of indusium.
aVitelline membranebBlastoderma.From T. W. Jones.
In those ova which are considerably developed before impregnation, the granular blastermodic membrane is observed to be thicker, and the granules more aggregated at that part which corresponds to the pedicle, forming a slight elevation with a depression in its centre, like the cumulus in the proligerous disc of a Graafian vesicle. This little disc is the blastoderma, germinial membrane or cicatricula; in the central depression just mentioned is an exceedingly minute vesicle first noticed by Professor Purkinje of Breslau, and named after him: in more correct language it is thegerminal vesicle.
According to Wagner, the germinal vesicle is not surrounded by a disc before impregnation; and it is only after this process that the above-mentioned disc of granules is formed. By the time the ovum is about to quit the ovary the vesicle itself has disappeared, so that an ovum has never been found in the oviduct containing a germinal vesicle, nothing remaining of it beyond the little depression in the cumulus of the cicatricula.
The rupture of the Purkinjean or germinal vesicle has been supposed by Mr. T. W. Jones to take place before impregnation; but the observations of Professor Valentin seem to lead to the inference that it is a result of that process, and must be therefore looked upon as one of the earliest changes which take place in the ovum or yelk-bag upon quitting the ovary.[24]
During its passing through the oviduct (what in mammalia is called the Fallopian tube,) the ovum receives a thick covering of albumen, and as it descends still farther along the canal the membrane of the shell is formed.
On examining the appearance of the ovum in mammiferous animals, and especially the human ovum, it will be found that it presents a form and structure very analogous to the ova just described, more especially those of birds. It is a minute spherical sac, filled with an albuminous fluid, lined with its blastodermic or germinal membrane, in which is seated the germinal vesicle or vesicle of Purkinje. When the ovum has quitted the ovary the germinal vesicle disappears, and on its entering the Fallopian tube it becomes covered with a gelatinous, or rather albuminous covering. This was inferred by Valentin, who considered that “the enormous swelling of the ova, and their passage through the Fallopian tubes,” tended to prove the circumstance. (Edin. Med. and Surg. Journ.April, 1836.) It has since been demonstrated by Mr. T. W. Jones in a rabbit seven days after impregnation. The vitellary membrane seems, at this time, to give way, leaving the vitellus of the ovum merely covered by its spherical blastoderma, and encased by the layer of albuminous matter which surrounds it.
From what we have now stated, a close analogy will appear between the ova of the mammalia and those of the lower classes, more especially birds, which from their size afford us the best opportunities of investigating this difficult subject.
In birds, the covering of the vitellus is calledyelk-bag; whereas, in mammalia and man it receives the name ofvesicula umbilicalis. Its albuminous covering, which corresponds to the white and membrane of the shell in birds, is calledchorion: by the time that the ovum has reached the uterus, this outer membrane has undergone a considerable change; it becomes covered with a complete down of little absorbing fibrillæ, which rapidly increase in size as development advances, until it presents that tufted vascular appearance, which we have already mentioned when describing this membrane.
The first or primitive trace of the embryo is in the cicatricula or germinal membrane, which contained the germinal vesicle before its disappearance. In the centre of this, upon its upper surface, may be discovered a small dark line;[25]“this line or primitive trace is swollen at one extremity, and is placed in the direction of the transverse axis of the egg.”
aTransparent area.bPrimitive trace.
As development advances, the cicatricula expands. “We are indebted to Pander,”[26]says Dr. Allen Thomson in his admirable essay above quoted, “for the important discovery, that towards the twelfth or fourteenth hour, in the hen’s egg the germinal membrane becomes divided into two layers of granules, the serous and mucous layers of the cicatricula; and that therudimentary trace of the embryo, which has at this time become evident, is placed in the substance of the upper-most or serous layer.” “According to this observer, and according to Baer, the part of this layer which surrounds the primitive trace soon becomes thicker; and on examining this part with care, towards the eighteenth hour, we observe that a long furrow has been formed in it, in the bottom of which the primitive trace is situated; about the twentieth hour this furrow is converted into a canal open at both ends, by the junction of its margins (theplicæ primitivæof Pander, thelaminæ dorsalesof Baer:) the canal soon becomes closed at the cephalic or swollen extremity of the primitive trace, at which part it is of a pyriform shape, being wider here than at any other part. According to Baer and Serres, some time after the canal begins to close, a semi-fluid matter is deposited in it, which on its acquiring greater consistence, becomes the rudiment of the spinal cord; the pyriform extremity or head is soon after this seen to be partially subdivided into three vesicles, which being also filled with a semi-fluid matter, gives rise to the rudimentary state of the encephalon.” “As the formation of the spinal canal proceeds, the parts of the serous layer which surrounds it, especially towards the head, become thicker and more solid, and before the twenty-fourth hour we observe on each side of this canal four or five small round opaque bodies, these bodies indicate the first formation of the dorsal vertebræ.
aTransparent area.bLaminæ dorsales.cCephalic end.dRudiments of dorsal vertebræ.eSerous layer.fLateral portion of the primitive trace.gMucous layer.hVascular layer.kLaminæ dorsales united to form the spinal canal.
“About the same time, or from the twentieth to thetwenty-fourth hour, the inner layer of the germinal membrane undergoes a farther division, and by a peculiar change is converted into the vascular mucous layers.” (A. Thomson,op. cit.) It will thus be seen, that the germinal membrane is that part of the ovum in which the first changes produced by impregnation are observed. The rudiments of the osseous and nervous systems are formed by the outer or serous layers; the outer covering of the fœtus or integuments, including the amnois, are also furnished by it. “The layer next in order has been calledvascular, because in it the development of the principal parts of the vascular system appears to take place. The third, called themucouslayer, situated next the substance of the yelk, is generally in intimate connexion with the vascular layer, and it is to the changes which these combined layers undergo, that the intestinal, the respiratory, and probably also the glandular systems owe their origin.” (A. Thomson,op. cit.p. 298.)
aSerous layer.b cVascular layer.dMucous layer.eHeart.
The embryo is therefore formed in the layers of the germinal membrane, and becomes, as it were, spread out upon the surface of the ovum: the changes which the ovum of mammalia undergoes appear from actual observation, to be precisely analogous to those in the inferior animals. (Baer,PrevostandDumas.) From the primitive trace, which was at first merely a line crossing the cicatricula, and which now begins rapidly to exhibit the characters of the spinal column, the parietes of the head and trunk gradually approach farther and farther towards the anterior surface of the abdomen and head until they unite; in this way the sides of the jaws close in the median line of the face, occasionally leaving the union incomplete, and thus appearing to produce in some cases the congenital defects of hare-lip and cleft palate. In some way the ribs meet at the sternum; and it may be supposed that sometimes this bone is left deficient, and thus may become one of the causes of those rare cases of malformation, where the child has been born with the heart external to the parietes of the thorax. In like manner the parietes of the abdomen and pelvis close in the linea alba and symphysis pubis, occasionally leaving the integuments of the navel deficient, or, in other words, producing congenital umbilical hernia, or at the pubes a non-union of its symphysis with a species of inversion of the bladder, the anterior wall of that viscus being nearly or entirely wanting.
The cavity of the abdomen is therefore at first open to the vesicula umbilicalis or yelk, but this changes as the abdominalparietes begin to close in; in man and the mammalia merely a part of it, as above mentioned, forms the intestinal canal, whereas, in oviparous animals the whole of the yelk-bag enters the abdominal cavity, and serves for an early nutriment to the young animal. Another change connected with the serous or outer layer of the germinal membrane is the formation of theamnion. The fœtal rudiment which from its shape has been calledcarina, now begins to be enveloped by a membrane of exceeding tenuity, forming a double covering upon it; the one which immediately invests the fœtus is considered to form the future epidermis; the other, or outer fold, forms a loose sac around it, containing the liquor amnii. Whilst these changes are taking place in the serous layer of the germinal membrane, and whilst the intestinal canal, &c. are forming on the anterior surface of the embryo, which is turned towards the ovum, by means of the inner or mucous layer, equally important changes are now observed in the middle or vascular layer. “In forming this fold,” says Dr. A. Thomson, “the mucous layer is reflected farthest inwards; the serous layer advances least, and the space between them, occupied by the vascular layer, is filled up by a dilated part of this layer, the rudiment of the heart.” (Op. cit.p. 301.)
Whilst this rudimentary trace of the vascular system is making its appearance, minute vessels are seen ramifying over the vesicula umbilicalis, forming, according to Baer’s observations, a reticular anastomosis, which unites into two vessels the vasa omphalo-meseraica. (British and Foreign Med. Rev.No. 1.) These may be demonstrated with great ease in the chick: the cicatricula increases in extent; it becomes vascular, and at length forms a heart-shaped net-work of delicate vessels, which unite into two trunks, terminating one on each side of the abdomen.
The umbilical vesicle now begins to separate itself more and more from the abdomen of the fœtus, merely a duct of communication passing to that portion of it which forms the intestinal canal. The first rudiment of the cord will be found at this separation; its fœtal extremity remains for a long time funnel-shaped, containing, besides a portion of intestine, the duct of the vesicula umbilicalis, the vasa omphalo-meseraica (the future vena portæ,) the umbilical vein from the collected venous radicles of the chorion, and the early trace of the umbilical arteries. These last-named vessels ramify on a delicate membranous sac of anelongated form which rises from the inferior or caudal extremity of the embryo, viz. theallantois; whether this is formed by a portion of the mucous layer of the germinal vesicle, in common with the other abdominal viscera, appears to be still uncertain: in birds this may be very easily demonstrated as a vascular vesicle, arising from the extremity of the intestinal canal; and in mammalia, connected with the bladder by means of a canal calledurachus: from its sausage-like shape, it has received the name ofallantois.
The existence of an allantois in the human embryo has been long inferred from the presence of a ligamentous cord extending from the fundus of the bladder to the umbilicus, like the urachus in animals. But from the extreme delicacy of the allantois, and from its function ceasing at a very early period, it had defied all research, until lately when it has been satisfactorily demonstrated in the human embryo by Baer and Rathke. It occupies the space between the chorion and amnion, and gives rise occasionally to a collection of fluid between these membranes, familiarly known by the name of the liquor amnii spurius, which, strictly speaking is the liquor allantoidis.
The function of the allantois is still in a great measure unknown. In animals it evidently acts as a species of receptaculum urinæ during the latter periods of gestation; but it is very doubtful if this be its use during the earlier periods. It does not seem directly connected with the process of nutrition, which at this time is proceeding so rapidly, first by means of the albuminous contents of the vitellus, or vesicula umbilicalis, and afterwards by the absorbing radicles of the chorion; but, from analogy with the structure of the lower classes of animals, it would appear that it is intended to produce certain changes in the rudimentary circulation of the embryo, similar to those which, at a later period of pregnancy, are effected by means of the placenta, and after birth by the lungs, constituting the great functions of respiration.
In many of the lower classes of animals, respiration (or at least the functions analogous to it) is performed by organs situated at the inferior or caudal extremity of the animal: thus for instance, certain insect tribes, as in hymenoptera, or insects with a sting, as wasps, bees, &c.; in diptera, or insects with two wings, as the common fly; and also the spider tribe, have their respiratory organs situated in the lower part of the abdomen. In some of the crustacea, as, for instance, the shrimp, the organs of respiration lie under the tail between the fins, and floating loosely in the water. Again, some of the molusca, viz. the cuttle-fish, have the respiratory organs in the abdomen. We also know that many animals, during the first periods of their lives, respire by a different set of organs to what they do in the adult state: the most familiar illustration of this is the frog, which, during its tadpole state, lives entirely in the water.
aBronchial processes.bVesiculaumbilicalis.cVitellus.dAllantois.eAmnion.From Baer.
As the growth of the embryo advances, other organs whose function is as temporary as that of the allantois, make their appearance: these also correspond to the respiratory organs of a lower class of animals, although higher than those to which we have just alluded,—we mean bronchial processes or gills. It is to Professor Rathke (Acta Naturæ Curios.vol. xiv,) that we are indebted for pointing out the interesting fact, that several transverse slit-like apertures may be detected on each side the neck of the embryo, at a very early stage of development. In the chick, in which he first observed it, it takes place about the fourth day of incubation: at this period the neck is remarkably thick, and contains a cavity which communicates inferiorly with the œsophagus and stomach, and opens externally on each side by means of the above-mentioned apertures, precisely as is observed in fishes, more especially the shark tribe; these apertures are separated from each other by lobular septa, of exceedingly soft and delicate structure. Rathke observed the same structure in the embryo of the pig and other mammalia; and Baer has since shown it distinctly in the human embryo. It is curious to see how the vascular system corresponds to the grade of development then present: the heart is single, consisting of one auricle and one ventricle; the aorta gives off four delicate, but perfectly simple branches, two of which go to the right, and two to the left side; each of these little arteries passes to one of the lobules or septa at the side of the neck, which correspond to gills, and having again united with the three others, close to what is the first rudiment of the vertebral column, they form a single trunk which afterwards becomes the abdominal aorta. In a short time these slit-like openings begin to close; the bronchial processes or septa become obliterated, and indistinguishable from the adjacent parts; the heart loses the form of a single heart; a crescentic fold begins to mark the future division into two ventricles, and gradually extends until the septum between them is completed. It is also continued along the bulb of the aorta, dividing it into two trunks, the aorta proper and pulmonary artery; at the upper part the division is left incomplete, so that there is an opening from one vessel to the other, which forms the ductus arteriosus.[27]A similarprocess takes place in the auricles, the foramen ovale being apparently formed in the same manner as the ductus arteriosus; these changes commence in the human embryo about the fourth week, and are completed about the seventh.
At first the body of the embryo has a more elongated form than afterwards, and the part which is first developed is the trunk, at the upper extremity of which a small prominence less thick than the middle part, and separated from the rest of the body by an indentation, distinguishes the head. There are as yet no traces whatever of extremities, or of any other prominent parts; it is straight, or nearly so, the posterior surface slightly convex, the anterior slightly concave, and rests with its inferior extremity directly upon the membranes, or by means of an extremely short umbilical cord.
The head now increases considerably in proportion to the rest of the body, so much so, that at the beginning of the second month, it equals nearly half the size of the whole body: previous to, and after this period, it is usually smaller. The body of the embryo becomes considerably curved, both at its upper as well as its lower extremity, although the trunk itself still continues straight. The head joins the body at a right angle, so that the part of it which corresponds to the chin is fixed directly upon the upper part of the breast; nor can any traces of neck be discerned, until nearly the end of the second month.
The inferior extremity of the vertical column, which at first resembles the rudiment of a tail becomes shorter towards the middle of the third month, and takes a curviture forwards under the rectum, in the fifth week the extremities become visible, the upper usually somewhat sooner than the lower, in the form of small blunt prominences. The upper close under the head, the lower near the caudal extremity of the vertebral column. Both are turned somewhat outwards, on account of the size of the abdomen; the upper are usually directed somewhat downwards, the lower ones somewhat upwards.
The vesicula umbilicalis may still be distinguished in the second month as a small vesicle, not larger than a pea, near the insertion of the cord, at the navel, and external to the amnion. Fromthe trunk, which is almost entirely occupied by the abdominal cavity, arises a short thick umbilical cord, in which some of the convolutions of the intestines may still be traced. Besides these it usually contains, as already observed, the two umbilical arteries and the umbilical vein, the urachus, the vasa omphalo-meseraica, or vein and artery of the vesicula umbilicalis, and perhaps, even at this period, the duct of communication between the intestinal canal and vesicula umbilicalis, the fœtal extremity of which, according to Professor Oken’s views, forms the processus vermiformis.
Diagram of the fœtus and membranes about the sixth week.
aChorion.bThe larger absorbent extremities, the site of the placenta.cAllantois.dAmnion.eUrachus.éBladder.fVesicula umbilicalis.gCommunicating canal between the vesicula umbilicalis and intestine.hVena umbilicalis.i iArteriæ umbilicales.lVena omphalo-meseraica.kArteria omphalo-meseraica.nHeart.oRudiment of superior extremity.pRudiment of lower extremity.From Carus.
The hands seem to be fixed to the shoulders without arms, and the feet to adhere to the ossa illi; the liver seems to fill the whole abdomen; the ossa innominata, the ribs, and scapulæ are cartilaginous.
In a short time the little stump-like prominences of the extremities become longer, and are now divided into two parts, the superior into the hand and the fore arm, the inferior into the foot and leg; in one or two weeks later, the arms and thighs are visible. These parts of the extremities which are formed later than the others, are at first smaller, but as they are gradually developed they become larger. When the limbs begin to separateinto an upper and lower part, their extremities become rounder and broader, and divided into the fingers and toes, which at first are disproportionately thick, and until the end of the third month are connected by a membranous substance analogous to the webbed feet of water birds; this membrane gradually disappears, beginning at the extremities of the fingers and toes, and continuing the division up to their insertion. The external parts of generation, the nose, ears, and mouth appear after the development of the extremities. The insertion of the umbilical cord changes its situation to a certain degree; instead of being nearly at the inferior extremity of the fœtus as at first, it is now situated higher up on the anterior surface of the abdomen. The comparative distance between the umbilicus and pubis continues to increase, not only to the full period of gestation, when it occupies the middle point of the length of the child’s body, as pointed out by Chaussier, but even to the age of puberty, from the relative size of the liver becoming smaller.
Though the head appears large at first, and for a long time continues so, yet its contents are tardy in their development, and until the sixth month the parietes of the skull are in great measure membranous or cartilaginous. Ossification commences in the base of the cranium, and the bones under the scalp are those in which this process is last completed.
The contents of the scull are at first gelatinous, and no distinct traces of the natural structure of the brain can be identified until the close of the second month; even then it requires to have been sometimes previously immersed in alcohol to harden its texture. There are many parts of it not properly developed until the seventh month. In the medulla spinalis no fibres can be distinguished until the fourth month. The thalami nervorum opticorum, the corpora striata, and tubercula quadrigemina, are seen in the second month; in the third, the lateral and longitudinal sinuses can be traced, and contain blood. In the fifth we can distinguish the corpus callosum; but the cerebral mass has yet acquired very little solidity, for until the sixth month it is almost semi-fluid. (Campbell’sSystem of Midwifery.)
About the end of the third, during the fourth, and the beginning of the fifth months, the mother begins to be sensible of the movements of the fœtus. These motions are felt sooner or later, according to the bulk of the child, the size and shape of the pelvis, and the quantity of fluid contained in the amnion, the waters being in larger proportionate quantity the younger the fœtus.
The secretion of bile, like that of the fat, seems to begin towards the middle of pregnancy, and tinges the meconium, a mucous secretion of the intestinal tube which had hitherto been colourless, of a yellow colour. Shortly after this the hair begins to grow, and the nails are formed about the sixth or seventhmonth. A very delicate membrane (membrana pupillaris,) by which the pupil has been hitherto closed, now ruptures, and the pupil becomes visible. The kidneys, which at first were composed of numerous glandular lobules (seventeen or eighteen in number,) now unite, and form a separate viscus on each side of the spine; sometimes they unite into one large mass, an intermediate portion extending across the spine, forming the horse-shoe kidney.
Lastly, the testes, which at first were placed on each of the lumbar vertebræ, near the origin of the spermatic vessels, now descend along the iliac vessels towards the inguinal rings, directed by a cellular cord, which Hunter has calledGubernaculum testis: they then pass through the openings carrying before them that portion of the peritoneum which is to form their tunica vaginalis.
The length of a full-grown fœtus is generally about eighteen or nineteen inches; its weight between six and seven pounds. The different parts are well developed and rounded; the body is generally covered with the vernix caseosa;[28]the nails are horny, and project beyond the tips of the fingers, which is not the case with the toes; the head has attained its proper size and hardness; the ears have the firmness of cartilage; the scrotum is rugous, not peculiarly red, and usually containing the testes. In female children the nymphæ are generally covered entirely by the labia, the breasts project, and in both sexes frequently contain a milky fluid. As soon as a child is born, which has been carried the full time, it usually cries loudly, opens its eyes, and moves its arms and legs briskly; it soon passes urine and fæces, and greedily takes the nipple. (Naegelé’sHebammenbuch.)
Thus, then, in the space of forty weeks, or ten lunar months, from an inappreciable point, the fœtus attains a medium length of about eighteen or nineteen inches, and a medium weight of between six and seven pounds. As these observations on the development of the ovum show that the structural arrangement of the embryo undergoes a succession of changes, by which it gradually rises from the lowest to the highest scale of formation, so we shall find it furnished with a succession of means for its nutrition, each corresponding more or less to the particular grade of development which it may have attained. Its earliest source of nourishment is doubtless the vitellus, or albuminous contents of the vesicula umbilicalis. The radicle or primitive trace, in this respect, bears a strong analogy to the seed of a plant; it brings with it its own supply of nourishment for its first stage ofgrowth; in the latter, the cotyledons afford nourishment to the little plumula, until, by the formation of roots and absorption of moisture from the surrounding soil, it is enabled to support the early rudiment of the future plant. The early function of the chorion is very analogous to that of roots; it is an absorbing apparatus, collecting nourishment by means of its numerous absorbing fibrillæ: hence, according to Lobstein, the umbilical vein exists for some time previous to the umbilical arteries, and seems to perform an office in the fœtus similar to that of the thoracic duct at a later period; its radicles or absorbing extremities seem to absorb a milky fluid, which after the first two months is found in the placenta, and which must be looked upon as a means of nourishment which does not exist in the latter months. This milky fluid was noticed by Leroux, who even then expressed his doubts, whether the radicles of the umbilical vein receive blood from the mother, or whether they only serve to absorb a white fluid which resembles chyle. In some manuscript notes of Dr. Young’s lectures, which were taken by the late Dr. Parry, of Bath, when a student at Edinburgh, we find the following observation: “There is evidently in the placenta, besides blood-vessels, some other substance, which serves to absorb juices from the uterus, and to convert these into a chylous matter proper to nourish the fœtus, and this matter is absorbed by the umbilical veins. This seems to be proved from the consideration of the placenta of animals which have cotyledons; for, on squeezing these glandular substances, we force out a sort of chylous liquor, and these are surrounded by the placenta, which absorb their liquor and convey it to the fœtus.”
The absorbing power of the umbilical vein continues till the fifth month; during the second or third, the fœtus receives a good deal of nourishment from the liquor amnii, which at this period contains a considerable quantity of albuminous matter; this diminishes in the latter months of pregnancy. Moreover the body of the fœtus begins to be covered with the vernix caseosa towards the seventh month, so that in the eighth and ninth months the absorption of liquor amnii by the skin is considerably impeded.
How far the full formed placenta, as seen after the fifth month, serves as a means of nutrition to the fœtus, may still be a matter of doubt; its chief use after this period is, as we have already shown, for the purpose of producing certain changes in the blood of the fœtus analogous to those of respiration;[29]still, however,it would seem that its function of nutrition is not entirely at an end, even at a late period of pregnancy. The numerous little granules of phosphate of lime, which are frequently found on the uterine surface of a full-grown placenta at a time when ossification is rapidly advancing in the fœtal skeleton, would surely lead us to infer that the placenta in some way or other supplies the materials for this process.
Fœtal circulation.We have already shown, that, in the early stages of development, the heart of the embryo is single, consisting of one auricle and one ventricle; that a septum gradually divides these into two parts until the double heart is formed, leaving two openings of communication between the right and left sides, the one between the auricles called theforamen ovale, the other between the pulmonary artery and aorta, viz. theductus arteriosus.
From these and other peculiarities it will be seen that the fœtal circulation differs essentially from that of a child after birth; and, in order to comprehend the nature and mechanism of the changes which take place in it when respiration first commences, it will be necessary that these peculiarities should be thoroughly understood. The condition of the fœtus must also be remembered: surrounded by the liquor amnii, the fœtus does not respire; its lungs have as yet been unemployed; they are therefore small and collapsed, and present a firm solid mass, nearly resembling liver in appearance. In this state but little blood from the pulmonary arteries can circulate through them; for, as the extreme ramifications of these vessels are distributed upon the mucous membrane lining the bronchi and air-cells, the free passage of blood through them will in great measure depend upon a previous condition of the air-cells. The pulmonary arteries in the fœtal state are therefore small, and transmit but a small quantity of blood into their numerous ramifications, just sufficient to keep pervious these vessels which after birth are to be so greatly distended: in this state the lungs when thrown into water sink.
Hence, as the pulmonary arteries do not afford a sufficiently free exit to the contents of the right side of the fœtal heart, nature has provided it with a peculiar means for carrying off the overplus quantity of blood, which is poured into the right auricle from the vena cava. This is attained first by theforamen ovale, an oval-shaped opening in the septum between the right and left auricles, and furnished with a semilunar valvular flap, so constructed, as to allow a free passage for the blood from the right to the left auricle, but none in the contrary direction. By this means a considerable quantity of blood is transmitted at once from the right to the left auricle, and, consequently, much less into the right ventricle and pulmonary artery. Still, however, more blood passes into the right ventricle than the pulmonary artery, in the collapsed state of the fœtal lungs, is capable of conveying away.The pulmonary artery is therefore continued beyond its bifurcation into the aorta at its curvature, by means of theductus arteriosus, which, in the full-grown fœtus, forms a short thick passage between these two vessels; and in this manner is the right ventricle enabled to get rid of its surplus quantity of blood. Thus we see that the fœtal heart although consisting of two auricles and two ventricles, continues to perform the functions only of a single heart, both ventricles assisting simultaneously to propel the same column of blood, viz. that of the aorta, and thus enabling the heart to act with considerable power.
The chief part of the blood, which flows through the iliac arteries, instead of being sent to the inferior extremities, is carried into the umbilical arteries, which passing up along the sides of the bladder meet the umbilical vein at the navel, and thus form the vessels of the umbilical cord. These arteries convey the blood of the fœtus to the placenta, where, having undergone changes to which we have already alluded, it is returned by the umbilical vein. This vessel, which afterwards forms the round ligament of the liver, passes through the umbilicus along the anterior edge of the suspensory ligament; it supplies the left lobe with blood, and having given off a communicating branch to the vena portæ, which supplies the right lobe, it passes at once by a short passage, calledcanalis venosus, into the vena cava.
Thus, then, the peculiarities of the fœtal circulation may be considered as four, viz. theforamen ovale, or passage from the right to the left auricle; theductus arteriosus, or communication from the bifurcation of the pulmonary artery into the arch of the aorta; theumbilical arteriesarising from the iliac arteries, and carrying the blood along the cord into the placenta; and, lastly, thecanalis venosus, or passage between the umbilical vein and vena cava.
Let us now examine the changes which take place in the fœtal circulation at the moment of the child’s birth. The child, which had hitherto been immersed in the bland and warm medium of the liquor amnii, is at once exposed to the action of the external air. By means of the sympathy existing between the skin and respiratory muscles, sudden and convulsive efforts at inspiration take place; the air-cells of the lungs become partially inflated, and, after a short time as the respiration increases in power and activity, become distended throughout their whole extent. The thorax rises; the flaccid diaphragm, which hitherto had been pushed up by the large fœtal liver, now contracts, pressing down the liver into its natural situation. The lungs, from being a hard solid heavy substance, resembling liver, at once become inflated, elastic, and crepitous, light and permeable to air in every part.
The capillary terminations of the pulmonary artery, which ramify in the mucous membrane, forming the parietes of theair-cells, and which hitherto had been firmly compressed by the collapsed state of the fœtal lungs, are suddenly rendered pervious throughout their whole extent. By this means, a vacuum, as it were, is formed in the ramifications of the pulmonary artery; each inspiration is accompanied by a rush of blood from the right ventricle into the newly-inflated structure. The pulmonary artery, at its bifurcation, swells and becomes turgid: the blood is carried off into its numerous ramifications as fast as the right ventricle can supply it; this may be easily understood from the law, in anatomy, viz. that the area of two arteries is greater than that of the trunk from which they bifurcate. From this state of distension, the distance between the pulmonary artery and the aorta is increased; the ductus arteriosus, which has now become empty, is stretched, and thus partially closed; the right auricle, which, but for the foramen ovale, could not have cleared itself of the whole quantity of blood which was poured into it from the vena cava, is now enabled to transmit its entire contents into the right ventricle; the left auricle, which before birth was supplied only by the foramen ovale from the right auricle, is now rapidly filled by the blood brought into it by the four pulmonary veins;—the equilibrium between the two auricles becomes altered;—the right, which hitherto had been somewhat gorged with blood, is now able to clear itself with facility; whereas, the left, which was but partially supplied, is now distended with a much greater quantity: there is now rather a disposition for the blood to regurgitate from the left to the right auricle; this, however, is prevented by the semilunar fold of the foramen ovale, which now acts as a valve, and generally becomes firmly attached to the septum. The obliteration of the canalis venosus at the posterior margin of the liver, and of the umbilical vein at the anterior edge, may, we think, be explained by the changes which necessarily follow the inflation of the lungs: the diaphragm, when it contracts, pulls down the liver into its natural situation; the distance, therefore, between the liver and the heart is increased, and the canalis venosus is consequently stretched, and considerably pressed upon, and precisely the same results follow with the umbilical vein.
NATURAL PREGNANCY AND ITS DEVIATIONS.
SIGNS OF PREGNANCY.
Difficulty and importance of the subject.—Diagnosis in the early months.—Auscultation.—Changes in the vascular and nervous systems.—Morning sickness.—Changes in the appearance of the skin.—Cessation of the menses.—Areola.—Sensation of the child’s movements.—“Quickening.”—Ausculation.—Uterine souffle.—Sound of the fœtal heart.—Funic souffle.—Sound produced by the movements of the fœtus.—Ballottement.—State of the uterine.—Violet appearance of the mucous membrane of the vagina.—Cases of doubtful pregnancy.—Diagnosis of twin pregnancy.
Difficulty and importance of the subject.—Diagnosis in the early months.—Auscultation.—Changes in the vascular and nervous systems.—Morning sickness.—Changes in the appearance of the skin.—Cessation of the menses.—Areola.—Sensation of the child’s movements.—“Quickening.”—Ausculation.—Uterine souffle.—Sound of the fœtal heart.—Funic souffle.—Sound produced by the movements of the fœtus.—Ballottement.—State of the uterine.—Violet appearance of the mucous membrane of the vagina.—Cases of doubtful pregnancy.—Diagnosis of twin pregnancy.
There is, perhaps, no subject connected with midwifery, which is of such importance, or which, from its difficulty and the serious questions it involves, demands such attentive consideration, and requires so familiar an acquaintance with every part of it, as the diagnosis of pregnancy. The responsibility which a medical man incurs in deciding cases of doubtful pregnancy, and in thus giving an opinion which may not only affect the fortune, happiness, character, but even life itself of the individual concerned, is rendered more painful by the perplexing obscurity of the circumstances under which these cases sometimes occur, being not unfrequently complicated with diseases which add still farther to the difficulty of coming at the truth, and occasionally rendered peculiarly obscure by wilful and determined falsehood and duplicity.
To render this subject more intelligible to our readers, we propose first to consider the general effects which pregnancy produces upon the system, and then to describe those changes and phenomena which arepeculiarto this state, and which may therefore be taken as so many means of diagnosis.
Under all circumstances, the diagnosis of pregnancy must ever be difficult and obscure during the early months; the development of the uterus is still inconsiderable, and the effects which it may have produced upon the system, although appreciable and even distinct, are nevertheless too capable of being also produced by other causes, to warrant our drawing any decided conclusion from them.
The effects over the whole animal economy, which result from the presence and advance of this great process, are very remarkable, and show themselves in every portion of it.
The vascular system undergoes a considerable change; the actual quantity of blood in the circulation appears to be increased; the pulse is harder, stronger, and more full; in many instances the blood, when drawn, exhibits the buffy coat, as in cases of inflammation; the vagina is more vascular, it is warmer, and the secretion of mucus considerably increased; there is a disposition to headach, and occasional flushing of the face; the animal heat over the whole body is increased. In the nervous system we also observe distinct evidences of a change having taken place: the irritability is increased; there is weariness, lassitude, and a peculiar alteration of taste and disposition; women, who otherwise are of a cheerful disposition, are now gloomy and reserved, andvice versâ; in some the temper becomes fretful and hasty, and in those who are naturally so, a most agreeable change for the better is sometimes observed.[30]Some are liable to spasmodic affections, palpitations, spasmodic cough, vomiting, fainting, headach, toothach, &c.: under this head will come the “morning sickness,” which is so commonly observed during the first weeks; the nature and treatment of which will be considered under theDiseases of Pregnancy; on the other hand, women who are constantly suffering from spasmodic affections, for instance, asthma, &c. are now entirely free from them, and appear to be insensible to causes which, in the unimpregnated state, would induce an attack. To changes in the nervous system must we, in great measure, attribute not only the sickness just mentioned, but also those extraordinary longings or antipathies for certain articles of food or drink, and in some cases, as in chlorosis, for substances which, underother circumstances, would excite disgust. In many, the changes in the function of the digestive apparatus does not amount to actual disease, the stomach merely refusing to digest articles of food which before had agreed with it: but in others, producing severe cardialgia, acidity, or even vomiting. Hence, we not unfrequently observe that women who had hitherto enjoyed a good digestion, now suffer from dyspepsia, and are obliged to be exceedingly careful in their diet; whereas those, in whom the digestion had been previously weak, are now able to digest almost any thing. The secretions of the whole alimentary canal are altered both in quality and quantity; the saliva frequently becomes tenacious, white, and frothy (Dewees,) and at times is so much increased in quantity as to amount to actual salivation; the secretions of the stomach are remarkably altered, as shown by the copious formation of acid in some cases during pregnancy; the mucus is ropy, and frequently vomited up in considerable quantities. The bowels are in some cases much relaxed; in others, constipated. This latter condition, however, may in part be attributed to the pressure of the gravid uterus obstructing the peristaltic motion.
The changes in the appearance of the skin during pregnancy are also worthy of notice. Women, who are naturally pale and of a delicate complexion, have frequently a high colour, andvice versâ; in some the skin assumes a sallow or cadaverous hue; copper-coloured blotches appear on the face and forehead: in others the skin appears loose and wrinkled, giving the patient an aged haggard expression, and destroying her good looks. Mole spots become darker and larger, and these, with a dark ring beneath the eyes and the changes already mentioned, combine to alter the whole appearance of the face. In some women a considerable quantity of hair appears in those parts of the face where the beard is seen in the other sex; it disappears after labour, when the skin resumes its natural functions, but returns on every succeeding pregnancy. In others a similar appearance takes place upon the breasts. The secretions of the skin are more or less altered; women who perspire freely have now a dry, rough skin; whereas those who at other times have seldom or never a moist skin, have copious perspiration, which is not unfrequently of a peculiarly strong odour. Cutaneous affections, also, which have been very obstinate, or had even become habitual, sometimes disappear, or at least are suspended during the period of utero-gestation. Similarly favourable changes are observed for a time in severe structural diseases of certain organs: the fact of well-marked phthisis apparently disappearing whilst pregnancy lasts, is well known.
The breasts become larger, blue veins are seen ramifying beneath the skin, and the circular disc of rose-coloured skin which surrounds the nipples becomes remarkably changed in colour, &c.;appearances, the description of which we shall defer until we come to the consideration of those phenomena produced by pregnancy, which may be looked upon as diagnostic.
The urine undergoes various changes; it is sometimes considerably increased, at others it is very high-coloured, or shows a peculiar milky sediment. A case has been quoted by Dr. Montgomery from Professor Osann’sClin. Rep.for 1833, p. 27., where the patient in three successive pregnancies was affected with diabetus mellitus, which each time completely ceased on delivery, and again returned when she became pregnant. None of the changes above enumerated excepting of those of the breasts, whether taken separately or conjointly, will enable us to form a correct diagnosis as to the existence of pregnancy. The appearance and feel of the abdomen during the early months afford no sure data: in fact, there is not a single symptom of pregnancy at this period, upon which we can rely with any degree of certainty.
Cessation of the menses.One of the most remarkable changes produced by pregnancy, and one which most constantly appears, is the cessation of the menstrual discharge. From its occurring so uniformly and so soon after conception, it is generally used by women as the best means of reckoning the duration of their pregnancy: still, however, it is very far from being a certain sign, and never can be depended upon by itself in forming our diagnosis. It is well known how many causes produce suppression of the catamenia, independent of pregnancy; and, on the other hand, ample experience has shown that suppressed catamenia are by no means a necessary consequence of pregnancy.
Although the fact has been contradicted by men of experience, still the regular appearance of the menses for the first few months of pregnancy is of such frequent occurrence as to place the matter beyond all doubt: in stating this, we do not allude to occasional discharges of blood from the vagina, but to regular periodical appearances of fluid distinctly bearing all the characters and peculiarities of the catamenia. This fact has been noticed so long ago, as by Mauriceau, who says, “I know a woman who had four or five living children, and who had with every child her menses from month to month, as at other times, only in a little less quantity, and was so till the sixth month, yet notwithstanding she was always brought to bed at her full time.”[31]
It is rare, however, to meet with the catamenia at so late a period, although cases do now and then occur where it lasts throughout pregnancy; more frequently it does not continue beyond the third or fourth month. The source of this dischargeappears to be from the vessels of the upper part of the vagina[32]and from the cervix uteri;[33]the gradually shortening of the latter as pregnancy advances may be considered as the reason why, in the majority of instances, the discharge diminishes after the second or third month, and usually ceases by the fifth or sixth. Dr. Dewees supports the same opinion with some excellent observations which are worthy of attention. “We are” says he “acquainted with a number of women who habitually menstruate during pregnancy until a certain period, but when that time arrives it ceases: several of these menstruated until the second or third months, others longer, and two until the seventh month; the last two were mother and daughter. We are certain there was no mistake in all the cases to which we now make reference. First, they (the menses) were regular in their returns, not suffering the slightest derangement from the impregnated condition of the uterus; 2. they employ from two to five days for their completion; 3. that the evacuation differed in no respect from the discharge in ordinary, except that they did not think it so abundant; 4. there were no coagula in any one of these discharges, consequently it could not be common blood of hæmorrhage; 5. in the two protracted cases, the quantity discharged regularly diminished after the fourth month, a circumstance perhaps not difficult of explanation.” (Compendious System of Midwifery, § 235.)
It occasionally happens that the first appearance of the catamenia after conception is more abundant than usual, a circumstance which had been noticed by Dr. W. Johnson in 1769, and confirmed by Dr. Montgomery in his admirable work on the signs of pregnancy, who also confirms the general fact of the menses occasionally appearing during pregnancy by his own experience, and by very ample references. (Op. cit.p. 46.)
The rarest and most extraordinary deviation of this kind from the usual course of things is the appearance of the mensesonly during pregnancy. Cases of this sort have been recorded by authors of the highest respectability, so that there can be no doubt as to the correctness of their statements. Thus, for instance, Baudelocque says, “I have met with several women, who assured me that they had not had their menses periodically except during their pregnancies; their testimony appeared to me to deserve more credit, because they only applied for an explanation of this extraordinary phenomenon.”[34]
By far the most interesting and detailed case of this nature isone described by Dr. Dewees. “A woman applied for advice for a long standing suppression of the menses; indeed she never had menstruated but twice. She had been married a number of months, and complained of a good deal of derangement of stomach, &c. We prescribed some rhubarb and steel pills; about six months after this she called to say that the medicine had brought down her courses, but that she was more unwell than before. The sickness and vomiting had increased, besides swelling very much in her belly; we saw this pretty much distended and immediately examined it, as we suspected dropsy; but from the feel of the abdomen, the want of fluctuation and the solidity of the tumour, we began to think it might be pregnancy, and told the woman our opinion. On mentioning our impression she submitted to an examination per vaginam; this proved her to be six months advanced in pregnancy. After this she had the regular returns of the catamenial period, until the full time had expired; during suckling she was free from the discharge. She was a nurse for more than twelve months; she weaned her child, and shortly after was again surprised by an eruption of the menses, which as on a former occasion proved to be a sign of pregnancy.” (Op. cit.§ 237.)
There are other circumstances also connected with the catamenia, which warn us against placing too much confidence in its disappearance as a sign of pregnancy: a woman may become pregnant who has never menstruated, a fact which has been noticed by several authors, and which has been explained as well as confirmed by Levret in hisArt des Accouchemens, § 230:—“A woman,” says he, “may conceive, although she has not yet menstruated, provided menstruation would otherwise have made its appearance shortly.”[35]
Another circumstance, of much more frequent occurrence, is the fact that a woman may become pregnant without having had a return of the menses since her last confinement; hence we occasionally meet with cases where, from a rapid succession of pregnancies, the menstruation has not appeared for several years. From what has now been said, it will be seen, beyond all doubt, thatthe non-appearance of the menses cannot be looked upon by itself as a diagnostic of pregnancy, orvice versâ: this is more particularly the case when any morbid condition of the system is also present; under such circumstances, little or no confidence can be placed upon it as a guide in forming our diagnosis. In cases where it is an object to conceal pregnancy, the appearance of the menstrual fluid upon the clothes has been imitated in order to deceive. (Montgomery,op. cit.p. 50.) Although, therefore, the cessation of the menses, when taken in connexion with other symptoms, will prove useful in assisting us to a correct opinion, nevertheless, when taken by itself, it will scarcely ever enable us to decide with certainty.
Areola.Among the earliest of those symptoms which must be considered as diagnostic are the changes observed in the appearance of the breasts; “they increase, become full; they are occasionally painful and grow hard: the veins in them are rendered conspicuous from their blue colour; the nipple becomes more bulky and appears inflated, its colour becomes darker, the surrounding disc undergoes a similar change, increases in extent, and is covered with little prominences like so many diminutive nipples.”[36]“The several circumstances (says Dr. Montgomery, p. 59,) here enumerated at least ought in all cases to form distinct subjects of consideration, when we propose to avail ourselves of this part as an indication of the existence or absence of pregnancy. One other, also, equally constant and deserving of particular notice, is a soft and moist state of the integument, which appears raised and in a state of turgescence, giving one the idea that if touched by the point of the finger it would be found emphysematous. This state appears, however, to be caused by infiltration of the subjacent cellular tissue, which together with its altered colour, gives us the idea of a part in which a greater degree of vital action is going forward than is in operation round it, and we not unfrequently find that the little glandular follicles, or tubercles, as they are called by Morgagni, are bedewed with a secretion sufficient to damp and colour the woman’s inner dress.
These changes do not take place immediately after conception, but occur in different persons after uncertain intervals. We must therefore consider, in the first place, the period of pregnancy at which we may expect to gain any useful information from the condition of the areola. I cannot say positively what may be theearliest period at which this change can be observed, but I have recognised it fully at the end of the second month, at which time the alteration in colour is by no means the circumstance most observable; but the puffy turgescence, though as yet slight, not alone of the nipple, but of the whole surrounding disc, and the development of the little glandular follicles, are the objects to which we should principally direct our attention, the colour at this period being in general little more than a deeper shade of rose or flesh colour, slightly tinged occasionally with a yellowish or light brownish hue. During the progress of the next two months the changes in the areola are in general perfected, or nearly so, and then it presents the following characters: a circle around the nipple, whose colour varies in intensity according to the particular complexion of the individual, being usually much darker in persons with black hair, dark eyes, and sallow skin, than in those of fair hair, light-coloured eyes, and delicate complexion.[37]The extent of this circle varies in diameter from an inch to an inch and a half, and increases in most persons as pregnancy advances, as does also the depth of the colour.”[38]
“In the centre of the coloured circle the nipple is observed partaking of the altered colour of the part, and appearing turgid and prominent, while the surface of the areola, especially that part of it which lies more immediately around the base of the nipple, is studded over, and rendered unequal by the prominence of the glandular follicles, which, varying in number from twelve to twenty, project from the sixteenth to the eighth of an inch; and lastly the integument covering the part appears turgescent, softer, and more moist than that which surrounds it; while on both there are to be observed at this period, especially in women of dark hair and eyes, numerous round spots, or small mottled patches of a whitish colour, scattered over the outer part of the areola, and for about an inch or more all round, presenting an appearance as if the colour had been discharged by a shower of drops falling on the part. I have not seen this appearance earlier than the fifth month, but towards the end of pregnancy it is very remarkable, and constitutes a strikingly distinctive character exclusively resulting from pregnancy. The breasts themselves areat the same time generally full and firm, at least more so than was natural to the person previously, and venous trunks of considerable size are perceived ramifying over their surface, and sending branches towards the disc of the areola, which several of them traverse along with these vessels. The breasts not unfrequently exhibit about the sixth month, and afterwards, a number of shining, whitish, almost silvery lines like cracks; these are most perceptible in women, who, having had before conception very little mammary development, have the breasts much and quickly enlarged after becoming pregnant.”
In enumerating these various changes which are observed in the breasts, we fully agree with Dr. Montgomery in saying, that the alteration in the colour of the areola is by no means that upon which we can depend with most certainty: in the first place, we frequently meet with so little discolouration during the earlier months as to be altogether inappreciable; we have also already shown that if the patient be a brunette, and has already had children, the colour of the areola cannot be trusted to, as it never entirely disappears after her first pregnancy. On the other hand, we occasionally meet with a considerable change of colour in the unimpregnated state, arising from uterine irritation, as in dysmenorrhœa, &c. Where, however, this is accompanied by the other changes above enumerated, there can be, we apprehend, no doubt as to the existence of the pregnancy. Dr. Smellie, and also Dr. W. Hunter both considered the areola as proof positive of pregnancy. The latter one decided upon a case of pregnancy under very extraordinary circumstances; the body of a young female was brought into the dissecting room, which at the first glance he pronounced to be pregnant, but the accuracy of his diagnosis was not a little doubted when it was ascertained that a perfect hymen was present: to decide the point he had the abdomen opened when the uterus was found to contain a small fœtus.
Movements of the fœtus.The sensation to the mother of the child moving in the uterus, cannot be looked upon as a certain sign of pregnancy, for even women who have had large families of children are frequently deceived in this respect by the movement of flatus in the intestines, by occasional spasmodic twitchings of the abdominal muscles, &c.; but when the motion of the child can be distinctly felt by the hand of an experienced practitioner, it will no longer admit of any doubt: this, however, is a symptom which can seldom be made use of before the middle of the sixth or seventh month.
Quickening.This leads us to the subject of quickening as a symptom of pregnancy. The very vagueness of the termquickeningis of itself a sufficient objection to its use as a source of information on these points. Strictly speaking, it refers to that moment of pregnancy when the woman is supposed to have becomequick with child, or in other words, when the fœtus becomesendued with life, “an error,” as Dr. Montgomery observes, “which the continued use of the term was obviously calculated to foster and to prolong” (p. 75.) As far as we can understand, the word “quickening” at the present day refers to two different events during pregnancy: the one is when the motion of the child first becomes perceptible to the mother; the other consists of those effects which are frequently observed when the uterus quits the pelvis, and rises into the abdominal cavity, viz. fainting, sickness, &c.; in either case it will be evident that no correct conclusion can be formed by this means. It may safely be asserted that until the last twenty years we possessed only three diagnostic marks of pregnancy, viz. the appearance of the areola, a series of changes but little understood; the being able to feel the movements of the child through the abdominal parietes, and the head of it per vaginam. Hence Dr. W. Hunter in describing the uncertainty of the signs of pregnancy says, “I find I cannot determine at four months, I am afraid of myself at five months, but when six or seven months are over, I urge an examination.”
In the primipara, the changes which pregnancy produces upon the os and cervix uteri are generally sufficient to lead to an accurate conclusion. The round dimple-like depression which the os uteri forms, the soft cushiony state of the cervix, are changes which we consider as peculiarly the effects of pregnancy, but their distinctness and certainty ceases when the patient has had several children; the irregular shape of the os uteri, its thickened edges, hard here and there, and the os tincæ, itself more or less open, the cervix scarcely, if at all, shortened, even at a late period of gestation, tend not a little to perplex the diagnosis furnished by this mode of examination; and where disease is complicated with pregnancy, the difficulty is greatly increased, and not unfrequently so much, that scarcely a single satisfactory point will be obtained.
Auscultation.Of late years, an immense advance has been made in the diagnosis of pregnancy, by means of the stethoscope. M. Major of Geneva,[39]in 1819, observed the interesting fact that he could hear the pulsations of the fœtal heart through the parietes of the mother’s uterus and abdomen: he appears, however, to have carried his researches no farther; and little attention was excited to the circumstance until three years afterwards, when a masterly essay on the subject was read before the Académie Royale de Médecine of Paris, by Lejumeau de Kergaradec.[40]In this interesting memoir, the author has described two sounds, which are perfectly distinct from each other in point ofcharacter. One of them consists of single pulsations, synchronous with those of the mother’s heart, accompanied with the deep whizzing rushing sound, which may be heard over a large portion of the uterus at once; the other of sharp, distinct, double pulsations, producing a ticking sound, and following a rythm, which is not synchronous with that of the maternal circulation. Kergaradec supposed that the former sound was produced by the circulation of the blood in the spongy structure of the placenta, and hence called it thesouffle placentaire; later observations[41]have, however, shown that it is not connected with the placenta, but depends upon the increased vascularity and peculiar arrangement of the uterine vessels during the gravid state. The other sound is produced by the pulsations of the fœtal heart.
Uterine souffle.The uterine sound, orsouffle, may invariably be heard in one or other of the inguinal regions, and usually over a considerable portion of the uterus, extending anteriorly or along the sides of the organ; and according to the observations of Professor Naegelé jun.,[42]there is no part of the uterus, capable of being osculted, in which this sound may not be heard. He considers that the souffle, which is so uniformly heard in the lower parts of the uterus, especially in the inguinal regions, seems to be produced by the uterine arteries before they enter the uterus; these vessels, as soon as they arrive at the broad ligament, assume a different character, become larger than they were on branching off from their original trunk, and are much contorted before entering the parietes of the uterus. Dubois first pointed out the similarity which exists between the sound heard in the gravid uterus, and that of aneurismal varix, where there is a direct passage of blood from an artery into a vein: the sound in this latter condition is produced by the current of blood rapidly issuing from the dilated artery, and mixing with the slower flowing stream of the dilated vein. The circulation of blood in the dilated arteries of the uterus present a considerable resemblance, in many respects, to that of the above-mentioned disease.
That the uterine sound is not confined to that part of the uterus where the placenta is attached, as was supposed by Professor Hohl,[43]is proved by the fact that we can frequently hear it in two different and sometimes opposite parts of the uterus at the same time, which, if his opinion be correct, would indicate the presence of twins; and yet the result of labour has proved that the uterus has contained but one child, and that the placenta had neither been attached in the one or other of these situations. The very circumstance which we have already mentioned, of this sound being invariably heard in one, if not in both, of the inguinal regions, shows that it is independent of the vicinity of theplacenta; nevertheless, it must be allowed, that as the uterine vessels undergo the greatest degree of development at this part, the sound will usually be at least as distinct here as in any other portion of the uterus.
The uterine souffle is the first sound which auscultation detects during pregnancy; it may be heard as early as the fifteenth or sixteenth week, but cases now and then occur where it has been even distinguished in the thirteenth or fourteenth week, and Dr. Evory Kennedy, has given some very interesting examples where he was able to hear it with certainty at the twelfth, eleventh, and even in one instance, at the tenth week. (Kennedy,op. cit.p. 80.) During these earlier periods, the sound is weaker, but extends over the whole uterus, from the diminutive size of which it can be heard most readily immediately above the symphysis pubis; in fact, there is every reason to suppose, that the uterine souffle might be detected at a still earlier period, if the uterus were at this time within reach of the stethoscope. As pregnancy advances, it becomes more distinct and powerful, and is occasionally so to a remarkably degree. During the latter periods of pregnancy, it frequently presents considerable modifications of tone, especially where there is general or local vascular excitement, as in cases of fever, or dispositions to hæmorrhage, where the vessels are usually distended, or where (Naegelé,op. cit.p. 86,) the placenta is situated near the os uteri, it assumes a piping, twanging sound of considerable resonance: the same is also observed where, either from the weight of the gravid uterus or any other cause, pressure has been exerted on any of the main arterial trunks: hence, as we shall show more fully when speaking of labour, a remarkable change is produced in the tone of the uterine souffle by the first contractions of that process. The causes of these modifications are not always very easily explained; we sometimes observe the souffle on the same side of the uterus vary rapidly in its degree of intensity, and occasionally even disappear for awhile without our being able to assign any satisfactory reason for such changes.
The uterine souffle taken by itself, although a very valuable sign of pregnancy, can scarcely be looked upon as one which is perfectly certain and diagnostic, since a similar sound may be produced by aneurism of the abdominal aorta and its large branches: there is much reason to think that the uterus, enlarged from other causes than that of pregnancy, and pressing upon the iliac arteries, will produce a similar sound. Professor Naegelé, jun., has also shown that the sounds of the patient’s heart may sometimes be heard very low in the abdomen, even as far as the ossa ilii, a circumstance which seems to have depended upon the sound being transmitted through the intestines distended with flatus. Where any of these causes of abdominal souffle have existed in connexion with suppressed catamenia, swelling of thebreasts, &c., we might be liable to be deceived if we allowed ourselves to be entirely guided by this sound.