(155.)Inflammation produced by Insects in the Air Passages.Much annoyance is caused to the sheep by the presence of animals in the air passages. TheŒstrus ovisdeposits its eggs on the margin of the nostril in autumn; these are soon hatched, and the larvæ immediately find their way up the interior of the nose, till they arrive at the frontal sinus, a cavity situated between the layers of the frontal bone, and of considerable size in the sheep. Here they remain till the following spring, when they quit their hold, become winged insects, and enter upon the career of torment so ably gone through by their predecessors.
ThePentastoma, an animal supposed at one time only to exist in the frontal sinus and lungs, and on the surface of the liver, of the dog, wolf, and horse, as well as in some reptiles, has been discovered by an able naturalist, my friend Mr Rhind of Edinburgh, in the frontal sinus of the sheep. It spends its whole existence there, and is distinguished from other entozoa by having the mouth between two pores on each side, through which a spicular process comes out. Figure 3, Plate VII. is taken from a drawing kindly furnished by Mr Rhind.
(156.)Removal of Insects from the Nostril.TheŒstrus ovisoccasions much distress to the sheep at the moment of depositing its eggs within the nostril. The animal on feeling the movements of the fly, rubs its nose against the ground, or, carrying it low, darts off at a rapid pace, vainly endeavouring to escape from its tormentor. During this period, a thin limpid fluid distils from the nostrils, leading a careless observer to confound the symptoms with those which accompany Coryza. In general the irritation is now terminated, as, while in the larvæ state, the insects are incapable of offensive measures. If they are clustered in considerable numbers in the frontal sinuses, they will doubtless lead to great suffering, parallel to what is recorded to have followed the nestling of insects in the same situation in the human being; and it is, therefore, advisable, when the cause of sturdy (paragraph 169) is in any way doubtful, first to apply those substances to the nostril, which are calculated to destroy both these larvæ and thepentastoma, should they happen to be there. Tobacco smoke is the only available remedy, and a very good one, being easily brought in contact with the worms, and, when properly administered, certain in its effects. One person secures the sheep holding the head in a convenient position, while another, having half filled a pipe with tobacco, and kindled it in the usual manner, places one or two folds of a handkerchief over the opening of the bowl, then passes the tube a good way up the nostril, applies his mouth to the covered bowl, and blows vigorously through the napkin. When this has continued for a few seconds, the pipe is withdrawn, and the operation repeated on the other nostril.
The round hair-worm (strongylus filaria) has been found in great numbers in the trachea and bronchii of calves by Camper, and of the sheep by Daubeuton. It has also been found in the reed and duodenum of the latter animal by Rudolphi. Two other species of the genusStrongle, theS. contortusandS. filicollis, have been detected in the sheep, the former in the belly, the latter in the small intestines. They all appear to originate only in such sheep as are exposed to the sapping influence of low damp situations, combined with stinted diet. Those occuring in the air tubes give rise to irritation, and a consequent harassing cough, which is only to be arrested by removing the sheep to a dry airy locality, and a nutritious pasture. Unless portions of the worms are thrown up during coughing, they cannot be pronounced with confidence to exist, as the symptoms which they produce are very similar to those which accompany the two following diseases.
(157.)Coryza.During the winter months, this affection is of very frequent occurence among sheep; but health is only in a few instances seriously affected. It is brought on by the exposure of the animal to intense cold, or to sudden chills, after it has been heated. In slight cases, the only annoyance to which the sheep is subjected, is from matter accumulating in the nostril, and plugging up the orifice, so that the poor creature is compelled to raise its head every three or four minutes, and labour hard for breath.[31]When the inflammation extends further down the air tubes, the symptoms assume a severer type, and death soon occurs, in general from suffocation. If the inflammation of the bronchial tubes becomes chronic, that is to say, if it goes on in a mild form for a length of time, pulmonary consumption (rot) will in all probability succeed, and destroy the sheep in a more lingering manner.
(158.)Treatment of Coryza.Should this disease prevail in a lenient form among your sheep, removal to a sheltered field, and a dose of purgative medicine, are all that is required. If, however, the feverish symptoms are severe, besides giving a purgative, bleed at the outset of the disease, and administer ten grains of the following fever powder, dissolved in a tea-cupful of warm water:—
Rub them well together, and divide the mixture into fifteen parts or powders. Half an hour after the powder is swallowed, give the sheep a basin of warm gruel, and repeat the powder at the end of six hours, if the symptoms are not considerably abated. When the sheep is recovering, keep it on juicy food, and do not expose it to inclement weather, as it will be very liable to another and more severe attack. Those sheep which are subject to cough on slight changes of temperature, should always be picked out, fattened for the market, and disposed of at the earliest opportunity, as they will, in all probability, sooner or later, fall victims to the following disease.
(159.)Rot.Every animal, from the serpent up to man, that is to say, every animal possessed of lungs, is liable torot. The inelegance of the term might be overlooked, provided a precise meaning were attached to it. Every one, however, seems to place some peculiar signification, and to hang some favourite theory, upon it, so that little wonder need be expressed either at the varying tenor of the treatment, or at the unsatisfactory conclusions which have been drawn regarding it. The word "rot," when employed in speaking of man, implies what, in popular language, is called "consumption," and is applied to that disease only when it affects the lungs. Thus the fork-grinders of Sheffield, who, from the nature of their employment, are much exposed to the exciting causes of consumption, and who, at an early age, fall victims to it, are said, by the people of that town, to die of rot. The term, however, so far as it has yet been used in relation to the sheep, has figured as the representative of a host of diseases, and, in becoming standard from frequent usage, has only rendered confusion worse confounded. "Rot," says the late Professor Coventry, in hisIntroductory Discourses, "is a word which has been employed to express a variety of disorders affecting this animal, with no small confusion and detriment. Indeed, in few instances has senseless indiscrimination done more mischief; for means inapt and injurious have been had recourse to, where skilful and timely interference would have had the happiest effects. Sheep are sometimes said to have the rot, when they labour underphthisis pulmonalis(consumption of the lungs), which they do but rarely; or under disorders of the liver, ashepatitis chronica, and that state of the same organ produced, or attended by thefasciolæ hepaticæ(fluke worms),hydatides, &c., which affections of the liver are not unfrequent. But the most common rot is still another and very distinct disorder, resembling, in many points, and probably the very same in its nature with,scorbutus(scurvy) in the human species, or thatmiseranda lues, that direful ruin of the general health and constitution, which silently supervenes from deficient or depraved aliment; and from which, as numerous observations testify, every flock, every sufferer, may be recovered by simple means seasonably used; but against which, in its advanced stage, all remedies prove of no avail. Perhaps, as the last symptoms of debility are very similar, and are most taken notice of by ordinary observers, the different kinds of rot might conveniently enough pass under the names of pulmonic, hepatic, and general rot."
Setting aside, for the moment, the inaccuracy of part of the above observations, I shall only remark, that, though Dr Coventry, in thus calling attention to the conflicting state of opinions on the subject, has accomplished much in reconciling discrepancies, he has still left something to be done in simplifying the matter; while he has, at the same time, rendered that something difficult of execution, from his own high authority being associated with the blunder. The only way, therefore, to remedy the thing, is to quit for the present the views of that learned gentleman, while I endeavour to give a plain account of the disease, its causes, and effects.
(160.)Symptoms of Rot.The first thing which indicates the presence of the disease, is the unwillingness of the affected animal to move about. It lags behind the flock, ascends a slope with difficulty, and has a listless, heavy, pithless appearance. Cough varying in frequency and violence, but extremely harassing, is present at every period of the disease, and is always increased on the slightest exertion.[32]At first this is accompanied by expectoration of the mucus of the air tubes; but in no long time purulent matter, indicative of more extensive inroads on the constitution, begins to be coughed up, and goes on increasing in quantity and becoming worse in quality till the termination of the disease. The wool becomes fine, white, thin, and brittle in the pile, and is easily brought away in masses by the slightest pull. The appetite is, throughout the disease, voracious, and though all the bad symptoms may be present, still the animal keeps up an appearance of plumpness. This, however, is hollow and deceitful, and the rapid loss of flesh which immediately succeeds, shows with what insidious certainty the malady has been progressing. Owing to the falling off in flesh and in fat, the neck appears to have acquired additional length, and the eyes to have sunk within the head. Sooner or later the skin beneath the neck becomes distended with serous fluid, and from this the disease has acquired the name ofPoke. The word, however, is far from applicable, as it might, with equal propriety, stand for any other disease attended with dropsical accumulations. Violent purging soon terminates the disease, death being generally preceded by the evacuation of a quantity of blackish matter.
(161.)Appearances on Dissection.The first thing which strikes a person on viewing the carcass of a sheep which has died of rot, is its leanness. In conducting the examination, the fell appears of a bluish white, the muscles are pale and wasted, and fat hardly to be met with. Where it once existed, a tough yellow substance alone remains, which is so destitute of all pretentions to the name of suet, that it cannot, even when thrown upon a fire, be made to blaze. Dropsical accumulations are found in the legs, chest, neck, and belly. On opening the chest, the lungs are often seen adhering at intervals to the lining membrane of the ribs, and have always a shrunk, diminutive appearance. These adhesions are frequently seen where there are no tubercles, and are in that case simply the result of exposure to cold; but where they are coincident with tubercles, they may be ascribed either to the animal having been exposed to cold, or to the inflammatory action set up by the tubercles themselves. The lungs are always the principal, and I may also, from my own experience, add, the primary seat of the affection. When examined in the early stage of rot, they have a hard lumpy feel, especially at the upper part or lobe, and at this time a great number of irregular yellowish white, patchy-looking bodies (PlateVI.fig. 2.), will be seen shining through the membrane,pleura, which surrounds the organ. Thesetubercles, as the hard white bodies are called, vary in size from that of a mustard seed to that of a pea. They are sprinkled through all parts of the lung, and will in every dissection, be found in a variety of stages, from the firm condition in which they were deposited, to the softened state which denotes their speedy expectoration. Each tubercle, however small, usually holds a particle of calcareous matter in its centre. The lungs, in the advanced stage of rot, will be full of cells or caverns, owing to the destruction of its texture by suppuration in those parts where tubercles existed. The cells or sacs are of all sizes, from that of a bean to that of a goose egg; but if the animal has been taken care of during the progress of the complaint, and lingered long, the abscesses will be so numerous, and so closely situated, as to give the remains of the lung the appearance of a large bag. Extreme cases of this nature are, however, rare; as the sheep, in general, either falls before the knife, or is killed from exposure to cold long ere the disease has reached its farthest limit. These sacs contain purulent matter, of all shades and odours, and identical with that which the animal coughed up.
Tubercles, and all their concomitants as above detailed, are also met with in the liver, though not so frequently as in the lungs. They constantly occur in theclyars(mesenteric or lacteal glands) which on this account are much above their usual size, and are occasionally found in other parts; but I need not proceed in their description, as sufficient has been said about them to enable the unprofessional reader to understand their relation to the complaints.
Fluke worms and hydatids are almost constant attendants on rot, and seemingly most important ones, especially the former, which have, I may say, kept a great bulk of the learned and unlearned for many years in a perpetual bustle, and have so effectually hoodwinked writers on this subject, as to prevent them seeing the truly important points in the disease. For this reason, I hold them worthy of particular description; as it is only by becoming acquainted with their history and habits that we can form correct ideas either of their mode of origin or of their supposed ability to cause rot.
(162.)The Liver Fluke(fasciola hepaticaordistoma hepaticum,Fig. 6.PlateI.) derives its name from the resemblance it bears to the plaice or flounder, though its shape has been more aptly compared to that of a melon seed. It is flat and oval, of a brownish-yellow colour, and varies in size from that of a pin-head to one inch in length, and half an inch in breadth. Each worm is bisexual or hermaphrodite, on which account they multiply with great rapidity. The generic name—distoma—signifies having two pores,a.b. Fig. 6, PlateI., and is for this reason applied to it. The nipple-like body at the extremitya.contains the orifice of the pore or opening leading to the female division of the generative apparatus, situated betweena.andb.In this cavity are formed the eggs, which are at intervals protruded, to be hatched when floating in the sheep's bile. The male organ is situated in front of the ventral pore. The anterior openingb.is equivalent to a mouth, and leads inwards and backwards, communicating with the intestinal canalsc., which are easily made out in the recent animal, from their containing dark bile, and which, as in other creatures low in the scale of being, serve the double purpose of a digestive and circulatory apparatus; that is to say, the stomach first prepares a fluid which is equivalent to blood, and then distributes it throughout the body.[33]
Flukes are never found in thearteriesof the liver, as has been erroneously stated by some writers, their abode being limited to the gall bladder and its ducts. In these they are often present in such numbers as to cause great distention of the sac and tubes, and in some instances the irritation produced by them leads to the thickening of the walls of the gall bladder, and to a deposition of calcareous matter between its coats; frequently also to complete obliteration of portions of the ducts. Hence the crackling sound sometimes perceived when handling the liver of a rotten sheep.
(163.)The Hydatid or Blob(Cysticercus tumicollis,Fig. 1.PlateVII.) so frequently found in sheep, is in form one of the simplest of the entozoa (literally dwellers within), being little more than a bag containing a quantity of fluid. As relates to outline, this hydatid bears no small resemblance to a Florence flask. It is said to have a head,h.—a neck,n.—a body,b.— and a posterior or caudal vesicle,c.v.Its claims to the title of an animal have been much disputed, but as it has been seen to move spontaneously, and as the contained fluid is always essentially different from that by which the hydatid is surrounded, the question may be looked upon as set at rest.[34]
The method of their reproduction is in unison with their structure, simple in the extreme. Nothing, however, very precise is known about the process. The vesicle which acts as heart and stomach serves also as the reproductive cavity, but how or by what means it is fecundated would be difficult to determine. The young hydatids are found adhering to the inner surface of the parent cavity. When they have attained maturity, the parent dies and shrivels, and the young ones begin to eliminate their nourishment from the juices of the quadruped which they infest.
These entozoa are found in general on the surface of the intestines, between them and their outer membrane (peritoneum), and on the exterior of the lungs and liver. They are always included in a cyst, to the inner surface of which they adhere by means of two hook-shaped processes projecting from the head. These cysts are always on the surface of the different viscera of the sheep, and in this way may be distinguished from another sacular animal, or rather supposed animal, termed acephalocyst or headless bag, which is sometimes found in clusters in the substance of the lungs, liver, &c. and is often confounded with the true hydatid.
(164.)Causes of Rot.If any one had been asked, thirty years ago, the cause or rather causes of the appearances which pass under the name of rot, he could not have enumerated them even in a day, for at that time each symptom was a disease, and as such was reckoned worthy of a separate and proximate cause. Nor could any person have had the courage to promulgate a common-sense opinion on the subject; for simple views regarding the diseases of domestic animals were then either not deemed worthy of a moment's notice, or, if considered, were swept at once, by the strong current of prejudice, into the foul ocean of predetermined disapproval. Opinions in cattle medicine were at that time valued according to the prolixity of their detail; and the more improbable the dependence of the effects upon the cause assigned, so much more was its discoverer lauded, and in like proportion was the chimerical fabric he had raised admired. Times are, however, now happily changed; that potent oculist, the march of intellect, has cleared the film from the public eye, and no one need, at present, be afraid to state the unaspiring fact, thattuberclesare the sole and proximate cause of the disease called rot.
The observations of the late Dr Coventry, already quoted, would lead us to suppose that tubercles are of rare occurrence in the lungs of sheep, but in refutation of this assertion, I need only request the reader to take a ramble through a butcher-market, and he will perceive, even on cursory inspection, the fallacy of this conclusion. What the state of the liver is which is attended with flukes and hydatids, he has left us to make out. Chronic hepatitis, which accompanies tubercles in the liver, goes for nothing as a disease of sheep, and therefore does not require a notice; besides, it is not rot, and is quite incompetent of itself to cause it. As for the scurvy of which he speaks, he evidently means the disease now generally known by the name ofPining, but which, as it has no connexion with rot, and has only become prevalent within the last sixteen years, could not be very well known to him.
The following questions will naturally occur to many of my readers. What gives rise to these tubercles? what are the predisposing causes which lead to their formation? and, when formed, how do these apparently unirritating bodies produce effects so baneful? Queries like these, however, cannot shortly be replied to, leading, as they do, to discussions which embrace many curious theories; but as the negative mode of teaching is often of avail where the positive or more direct would fail to bring conviction, I shall, before proceeding to allude to what the causes are, endeavour to state what they are not.
Imaginary Causes of Rot.The liver-fluke has long been looked upon as the origin of rot, and this opinion has now become so deeply rooted, and taken so fast a hold of the public mind, that if I were to contradict it by plain assertion, I should only be striving to buffet singly a tide of opposition. The best way, therefore, will be to examine a few of the theories supposed to be confirmatory of the notion that fluke worms are the beginning of the mischief, and then see whether their supporters have managed to make good the point.
I. The fluke is supposed to get into the liver of the sheep by being swallowed, and this, according to our theorists, may be brought about in some of the following ways:—1. The eggs may be floating in the air, and thus accidentally reach their destination. This is the view taken by the celebrated Clater; but if he had been, in this instance, a man of experiment, rather than of idle conjecture, he would have found, as any one readily may, that the eggs of the fluke worm sink in water, and, consequently, that they cannot float in air.[35]2. The Rev. Dr Singer, to whom Scotland at large, and Dumfries-shire in particular, is much indebted for numerous and valuable papers on agricultural subjects, states, in the third volume of theHighland Society's Transactions, page 478, that "The spawn or eggs of the liver fluke are most probablyconveyed upon the grassby summer watering, and afterwards taken into the stomach with it." A few lines further on, he speaks of the eggs being "wafted thither by harvest waterings." Now, as the fluke is only produced within the sheep, I need only put the unanswerable questions—How are they conveyed to the grass? and from whence are they wafted? to refute at once this hasty notion.3. The eggs may be voided by the sheep, may fall upon the herbage, and there remain till they are eaten. Such is the supposition published by Mr King of Hammersmith, in theQuarterly Journal of Agriculture, No. XXXI. p. 331, in which, after showing the vast number of eggs which must fall upon the grass, he says, "We must cease to wonder that so many sheep die of rot; the miracle is, that every sheep does not die of it."! I cannot, however, for my part, see a miracle in the matter, for the simple reason, that the eggs of the entozoa are not capable of retaining their vitality when absent even for a very short time from the place of their nativity, and therefore may be eaten with impunity.II. Supposing the eggs to have reached the sheep's stomach in a condition to allow of their being hatched, they, according to popular voice, find their way into the gall bladder by one of two routes.1. Mr King, the gentleman above spoken of, conjectures, in the same paper, that the fluke, after leaving the egg in the stomach of the sheep,makes its way up the gall vessels. This is, I am sorry to say, a very idle conjecture, as, from the valvular nature of the opening of the gall duct into the duodenum, an entrance from that intestine to the gall bladder is perfectly impracticable to any of the entozoa.[36]2. The eggs are believed by a writer in theLetters of the Bath Society of Agriculture, for 1781, to be taken into the blood along with the chyle from the small intestines, and to be arrested in the liver by the secretory ducts. This, it must be clear to every one, is the most absurd of all the notions; for if a globule of blood, which we must suppose to be the largest body capable of being absorbed from the intestine, is only about 1/3000 of an inch in diameter, how can the egg of a fluke worm pass through the same channel, when Mr King has, by careful observation, shown it to be 1/300 an inch in its shortest measurement. Again, allowing that they are taken into the blood, would they not frequently be hatched there, and would they not also be found in other quarters besides the liver. But do we ever find them in the blood? Do we ever see them in other organs? Certainly not.Not one of these theories would ever have been broached had their authors been aware of two important circumstances. 1. That M. Schreiber, the director of the Museum at Vienna, has proved that worms and their ova are not capable, under ordinary circumstances, of resisting the action of the digestive organs, and, therefore, that they cannot be introduced into the body by this channel. "During six months, he fed a pole-cat almost exclusively on various kinds of intestinal worms, and their eggs mixed up with milk; and on killing and examining it, at the end of this period, not a single worm of any kind was found in it."[37]The reader may perhaps object to this illustration, on the ground that there is so vast a difference between a sheep and a pole-cat, that a comparison in regard to their digestive habits cannot possibly hold good, but if he will turn to paragraph (96), he will see that the stomach of a sheep is as well fitted as that of a carnivorous quadruped for the digestion of animal matters. 2dly, the fluke worm has been found by Frommen in the fœtus of the sheep, into which it could not have been conveyed by transmission from the mother, as there is no direct vascular communication between the fœtal and maternal side.From a consideration of all these data, the conclusion must at once be drawn, that as living flukes cannot reach the liver from without, they must of a necessity be produced only in particular states of the animal they inhabit. How they originate we cannot of course determine, and this is not the place to hazard physiological conjectures; but it will be found that their appearance in the bile is always preceded by tuberculous deposits in the lungs or liver. This I have proved by numerous dissections, in which I have occasionally found tubercles without flukes, but never met with flukes where I did not at the same time discover tubercles. Fluke worms, therefore, can never be regarded as a cause of rot, they must be looked upon merely as a symptom. We cannot, however, say that tubercles give rise to the liver-fluke, for tubercles are often present in cases where flukes are absent; and if the latter were the effect of the former, their presence under such circumstances would in all probability be constant.III. Particular plants have been said to cause rot, but the proofs of their evil tendencies being in every instance about as logically supported as the fluke theories already mentioned, I need not trouble myself or the reader by proceeding to details.
I. The fluke is supposed to get into the liver of the sheep by being swallowed, and this, according to our theorists, may be brought about in some of the following ways:—
1. The eggs may be floating in the air, and thus accidentally reach their destination. This is the view taken by the celebrated Clater; but if he had been, in this instance, a man of experiment, rather than of idle conjecture, he would have found, as any one readily may, that the eggs of the fluke worm sink in water, and, consequently, that they cannot float in air.[35]2. The Rev. Dr Singer, to whom Scotland at large, and Dumfries-shire in particular, is much indebted for numerous and valuable papers on agricultural subjects, states, in the third volume of theHighland Society's Transactions, page 478, that "The spawn or eggs of the liver fluke are most probablyconveyed upon the grassby summer watering, and afterwards taken into the stomach with it." A few lines further on, he speaks of the eggs being "wafted thither by harvest waterings." Now, as the fluke is only produced within the sheep, I need only put the unanswerable questions—How are they conveyed to the grass? and from whence are they wafted? to refute at once this hasty notion.3. The eggs may be voided by the sheep, may fall upon the herbage, and there remain till they are eaten. Such is the supposition published by Mr King of Hammersmith, in theQuarterly Journal of Agriculture, No. XXXI. p. 331, in which, after showing the vast number of eggs which must fall upon the grass, he says, "We must cease to wonder that so many sheep die of rot; the miracle is, that every sheep does not die of it."! I cannot, however, for my part, see a miracle in the matter, for the simple reason, that the eggs of the entozoa are not capable of retaining their vitality when absent even for a very short time from the place of their nativity, and therefore may be eaten with impunity.
1. The eggs may be floating in the air, and thus accidentally reach their destination. This is the view taken by the celebrated Clater; but if he had been, in this instance, a man of experiment, rather than of idle conjecture, he would have found, as any one readily may, that the eggs of the fluke worm sink in water, and, consequently, that they cannot float in air.[35]
2. The Rev. Dr Singer, to whom Scotland at large, and Dumfries-shire in particular, is much indebted for numerous and valuable papers on agricultural subjects, states, in the third volume of theHighland Society's Transactions, page 478, that "The spawn or eggs of the liver fluke are most probablyconveyed upon the grassby summer watering, and afterwards taken into the stomach with it." A few lines further on, he speaks of the eggs being "wafted thither by harvest waterings." Now, as the fluke is only produced within the sheep, I need only put the unanswerable questions—How are they conveyed to the grass? and from whence are they wafted? to refute at once this hasty notion.
3. The eggs may be voided by the sheep, may fall upon the herbage, and there remain till they are eaten. Such is the supposition published by Mr King of Hammersmith, in theQuarterly Journal of Agriculture, No. XXXI. p. 331, in which, after showing the vast number of eggs which must fall upon the grass, he says, "We must cease to wonder that so many sheep die of rot; the miracle is, that every sheep does not die of it."! I cannot, however, for my part, see a miracle in the matter, for the simple reason, that the eggs of the entozoa are not capable of retaining their vitality when absent even for a very short time from the place of their nativity, and therefore may be eaten with impunity.
II. Supposing the eggs to have reached the sheep's stomach in a condition to allow of their being hatched, they, according to popular voice, find their way into the gall bladder by one of two routes.
1. Mr King, the gentleman above spoken of, conjectures, in the same paper, that the fluke, after leaving the egg in the stomach of the sheep,makes its way up the gall vessels. This is, I am sorry to say, a very idle conjecture, as, from the valvular nature of the opening of the gall duct into the duodenum, an entrance from that intestine to the gall bladder is perfectly impracticable to any of the entozoa.[36]2. The eggs are believed by a writer in theLetters of the Bath Society of Agriculture, for 1781, to be taken into the blood along with the chyle from the small intestines, and to be arrested in the liver by the secretory ducts. This, it must be clear to every one, is the most absurd of all the notions; for if a globule of blood, which we must suppose to be the largest body capable of being absorbed from the intestine, is only about 1/3000 of an inch in diameter, how can the egg of a fluke worm pass through the same channel, when Mr King has, by careful observation, shown it to be 1/300 an inch in its shortest measurement. Again, allowing that they are taken into the blood, would they not frequently be hatched there, and would they not also be found in other quarters besides the liver. But do we ever find them in the blood? Do we ever see them in other organs? Certainly not.Not one of these theories would ever have been broached had their authors been aware of two important circumstances. 1. That M. Schreiber, the director of the Museum at Vienna, has proved that worms and their ova are not capable, under ordinary circumstances, of resisting the action of the digestive organs, and, therefore, that they cannot be introduced into the body by this channel. "During six months, he fed a pole-cat almost exclusively on various kinds of intestinal worms, and their eggs mixed up with milk; and on killing and examining it, at the end of this period, not a single worm of any kind was found in it."[37]The reader may perhaps object to this illustration, on the ground that there is so vast a difference between a sheep and a pole-cat, that a comparison in regard to their digestive habits cannot possibly hold good, but if he will turn to paragraph (96), he will see that the stomach of a sheep is as well fitted as that of a carnivorous quadruped for the digestion of animal matters. 2dly, the fluke worm has been found by Frommen in the fœtus of the sheep, into which it could not have been conveyed by transmission from the mother, as there is no direct vascular communication between the fœtal and maternal side.From a consideration of all these data, the conclusion must at once be drawn, that as living flukes cannot reach the liver from without, they must of a necessity be produced only in particular states of the animal they inhabit. How they originate we cannot of course determine, and this is not the place to hazard physiological conjectures; but it will be found that their appearance in the bile is always preceded by tuberculous deposits in the lungs or liver. This I have proved by numerous dissections, in which I have occasionally found tubercles without flukes, but never met with flukes where I did not at the same time discover tubercles. Fluke worms, therefore, can never be regarded as a cause of rot, they must be looked upon merely as a symptom. We cannot, however, say that tubercles give rise to the liver-fluke, for tubercles are often present in cases where flukes are absent; and if the latter were the effect of the former, their presence under such circumstances would in all probability be constant.
1. Mr King, the gentleman above spoken of, conjectures, in the same paper, that the fluke, after leaving the egg in the stomach of the sheep,makes its way up the gall vessels. This is, I am sorry to say, a very idle conjecture, as, from the valvular nature of the opening of the gall duct into the duodenum, an entrance from that intestine to the gall bladder is perfectly impracticable to any of the entozoa.[36]
2. The eggs are believed by a writer in theLetters of the Bath Society of Agriculture, for 1781, to be taken into the blood along with the chyle from the small intestines, and to be arrested in the liver by the secretory ducts. This, it must be clear to every one, is the most absurd of all the notions; for if a globule of blood, which we must suppose to be the largest body capable of being absorbed from the intestine, is only about 1/3000 of an inch in diameter, how can the egg of a fluke worm pass through the same channel, when Mr King has, by careful observation, shown it to be 1/300 an inch in its shortest measurement. Again, allowing that they are taken into the blood, would they not frequently be hatched there, and would they not also be found in other quarters besides the liver. But do we ever find them in the blood? Do we ever see them in other organs? Certainly not.
Not one of these theories would ever have been broached had their authors been aware of two important circumstances. 1. That M. Schreiber, the director of the Museum at Vienna, has proved that worms and their ova are not capable, under ordinary circumstances, of resisting the action of the digestive organs, and, therefore, that they cannot be introduced into the body by this channel. "During six months, he fed a pole-cat almost exclusively on various kinds of intestinal worms, and their eggs mixed up with milk; and on killing and examining it, at the end of this period, not a single worm of any kind was found in it."[37]The reader may perhaps object to this illustration, on the ground that there is so vast a difference between a sheep and a pole-cat, that a comparison in regard to their digestive habits cannot possibly hold good, but if he will turn to paragraph (96), he will see that the stomach of a sheep is as well fitted as that of a carnivorous quadruped for the digestion of animal matters. 2dly, the fluke worm has been found by Frommen in the fœtus of the sheep, into which it could not have been conveyed by transmission from the mother, as there is no direct vascular communication between the fœtal and maternal side.
From a consideration of all these data, the conclusion must at once be drawn, that as living flukes cannot reach the liver from without, they must of a necessity be produced only in particular states of the animal they inhabit. How they originate we cannot of course determine, and this is not the place to hazard physiological conjectures; but it will be found that their appearance in the bile is always preceded by tuberculous deposits in the lungs or liver. This I have proved by numerous dissections, in which I have occasionally found tubercles without flukes, but never met with flukes where I did not at the same time discover tubercles. Fluke worms, therefore, can never be regarded as a cause of rot, they must be looked upon merely as a symptom. We cannot, however, say that tubercles give rise to the liver-fluke, for tubercles are often present in cases where flukes are absent; and if the latter were the effect of the former, their presence under such circumstances would in all probability be constant.
III. Particular plants have been said to cause rot, but the proofs of their evil tendencies being in every instance about as logically supported as the fluke theories already mentioned, I need not trouble myself or the reader by proceeding to details.
Real Causes of Rot.Everything that has a tendency to weaken the animal, will be more or less liable to lead to rot. Exposure to cold and wet, mishaps at lambing time, food bad in quality or deficient in quantity, and over-driving, will all predispose the constitution to the deposition of tubercles. It is from the causes being in this way common to the whole flock, that contagious properties have been ascribed to rot, it having been observed, from the time of Virgil, to break out in many animals at once.[38]
The reason of so many different things having, from first to last, been reckoned capable of producing this disease, appears to lie in the known fact, that if a sheep be exposed to any of the above depressing agents, rot, if the animal be as yet untainted, will not, at the moment, shew itself; but a chain of morbid actions will in all probability then commence, and, being beyond the ken of ordinary observers, will pass unheeded, till some slight mismanagement in food or shelter, hastens their progress, and renders them apparent to the plainest understanding. The final symptoms of rot may thus occur on any kind of pasture, and the scene of the catastrophe will incur a stigma which ought to be attached to herbage which the sheep have consumed at some distant place or date.
Bad food is justly regarded as one of the most common causes of rot, and ranks, in my estimation, next to cold and wet, in its power of producing it. I shall only remark, on this point, that of all the food on which sheep can possibly be kept, none is known to act so deleteriously as grass which has sprouted quickly. Rot is well known to occur most frequently on land which has been irrigated during summer, for at this season any excess of moisture is peculiarly injurious to the economy of a plant.
When plants by heat and moisture are stimulated to increased exertion on a poor soil, they acquire bulk without having it in their power to obtain at the same time those saline matters which constitute a healthy plant, becoming in fact, to the eye of an inexperienced person, thriving vegetables, while to the palate they prove wersh and watery.
The same result may follow from a different process. The saline matter may not be taken up, even when the soil is rich in such ingredients, from the functional derangement into which the roots or digestive organs have been thrown by the unnatural circumstances in which it has been placed. A plant is composed, like all organized bodies, of a certain number of proximate principles, which are more or less numerous in different kinds. These are combined with varying quantities of potass, soda, lime, magnesia, and iron, which, though formerly supposed to be too trifling in quantity materially to affect the quality of the plant, have yet been recently and satisfactorily proved completely to change the character of the compound, even when the excess or deficiency amounts only to a 1/10000th part so that, supposing an animal to thrive on plants which contain salts of any or all of the above bodies, it will soon fall off if these plants are in any way deprived of a single adjunct; for by the removal of that one salt, their nature has been entirely altered.
The certainty and rapidity with which Bakewell could rot his sheep, by pasturing them, in Autumn, on land over which water had been allowed to flow during the previous summer, may seem to controvert what I have above stated, as to time and frequent change of pasture often intervening between the origin of the disease, and its termination; but when it is recollected that he pursued the destructive system of breedinginandin, of itself sufficient to induce a tuberculous predisposition, the reader will perceive that his sheep were, in all likelihood, more or less tainted, and therefore, sure to fall victims to the disease the moment they were subjected to the deleterious influence of an unwholesome pasture.[39]
Over-driving and hurrying of every kind, is, in my opinion, a fruitful source of rot, not only from the fatigue it causes, or the risk it leads to of taking cold, but also from the injury, which in many cases results, to the delicate texture of the lungs. As shown in the note to paragraph (157), no animal is more easily put out of breath by running, than the sheep. Whenever the breathing is hurried, the circulation through the lungs is quickened also. If the tissue of the lungs be in any way delicate, the force with which the blood is propelled is sure to make it yield, and in this manner the animal is often suffocated by the large quantity of blood, which issues into the air tubes at once from many points. Fig. 1, Plate VI. exhibits a good illustration of this taken from a sheep. Numerous red points are seen sprinkled over the surface of the section, indicating that blood has been effused from many minute torn vessels. Now, if this animal had survived, each speck of blood would have formed a centre, round which tuberculous matter, as in Fig. 2, Plate VI. would have been secreted, and death from rot, at some ulterior period, would, in all probability, have been the result.[40]
(165.)Treatment of Rot.As reason and experience have taught us that tathy herbage is a common cause of this complaint, we should, when it shows itself, at once remove the animals to a better pasture, where they should be exempted from teazing of every kind.
Salt appears, after every trial, to be the best medicine, and to this they should have, at all times, ready access. Should the disease be rather far advanced, the breathing hurried, and the cough annoying, occasional doses of the following infusion will be of service, in enabling the farmer to keep down the disease, till such time as he can conveniently dispose of the animal.
pour the water on the leaves, cover up the vessel, and keep it in a warm place for six or eight hours, then strain.
Two tea-spoonfuls morning and evening may be given to a sheep, but as the plant is an active poison, and the strength of its infusion liable to vary, a couple of days should always intervene between every six doses.
About the year 1800, a notion prevailed in this country, that an effectual remedy for rot had been discovered by the Dutch, but this was quite unfounded, nocureever having been hit upon for this sweeping malady; indeed, a cure is fairly out of the question: its prevention and palliation, but not its eradication, being all that we can hope for. Sundry plausible plans of treatment have, however, at one time or another been contrived, some of them, in all conscience, harmless enough, but others again as well adapted for the destruction of the animal, as the removal of the disease.
As fluke worms have usually been reckoned the cause of rot, so the treatment has principally consisted in attempts to effect their extermination. With this view, Sir George Steuart Mackenzie of Coule, in defiance of all preconceived medical opinion, advocated, in his work onSheep, published in 1809, the employment of mercury to stay the progress of rot, and in the same work,or one very like it, as lately published anonymously by the Society for the Diffusion of Useful Knowledge, under the title of theMountain Shepherd's Manual, the utility of this dangerous procedure is as firmly maintained. At the same time Sir George, though rather in the dark as to the real nature of the disease, admits, in both editions, that tubercles exist in rot, especially in the lungs. Now, if he had inquired of any medical person what drug ought, when tubercles are present, of all others to be avoided, he would have found that medicine to be mercury. The administration of it therefore in rot, no matter what may be the form or mode in which it is exhibited, will to a certainty aggravate the symptoms, and shorten life. If, for the sake of doing something, you willendeavourto remove the worms, Chabert's animal oil will be found a safe and efficacious remedy; but, if my opinion can have any weight, I would recommend the farmer to allow them to remain.
Sheep, when displaying symptoms of rot, should always be kept dry and warm. If they must be retained throughout the winter, good sound solid food, such as well made hay or oats, should be afforded them, and the shelter of a straw yard should if possible be obtained. A liberal supply of salt should be given with all their provender; and if they do not seem to relish it, give them occasionally a small quantity in water as a drench.
(166.)Prevention of Rot.On this head I need do little more than remark that attention to the causes will go a great way to point out the necessary means for its prevention. Admission of the sheep to rank soft grass, heavy stocking, short allowance of food during winter, every thing in fact which leads to the exposure of the animal should be scrupulously avoided. The strongest constitution cannot with impunity be tampered with, and the soundest habit will fall before the mining attacks of want and weather. Keep your stock always in as high health as possible, for such is the surest prevention of tuberculous disease.
As rot is hereditary,[41]1 the importance of weeding out ewes from the flock on their first exhibiting appearances of unsoundness, is acknowledged by all. Many ways have been pointed out for detecting the incipient symptoms, but none plainer and better than those written by the late Mr Beattie of Muckledale, and published in the 3d vol. of theHighland Society's Transactions. "The first thing to be observed," says Mr Beattie, "is in the spring, when they are dropping their lambs. A sound ewe, in good order, drops a lamb covered with a thick and yellow slime, which the ewe licks off it, and the rule is, the sounder and the higher the condition the ewe is in, the darker and thicker will be the slime; but when they observe a ewe drop a lamb covered with thin watery bubbles, and very white, they note her down as unsound."
"About the month of September, when they intend to dispose of their draught ewes, they put all their sheep into a fold, and draw them by the hand, that is, they catch them all, viz. the ewes they design to sell any of, and clapping their hand upon the small of the back, they rub the flesh backwards and forwards between their fingers and thumb and the ends of the short ribs: if the flesh be solid and firm, they consider her as sound; if they find it soft and flabby, and if, when they rub it against the short ribs, it ripples, as we term it, that is, a sort of crackling is perceived, as if there were water or blubber in it, they are certain she is unsound. This is the most certain of all symptoms, but is not to be discerned with any degree of certainty but by an experienced hand; for although, as I have here related it, it seems a very simple affair, and easily acquired, yet it is well known that many shepherds, who have followed sheep all their lives, never arrived at any thing like certainty in judging by the hand, whilst men of superior skill will seldom be mistaken, and will draw by no other rule. Yet still it must be acknowledged that the seeds of this disease will sometimes lie so occult, as to baffle all skill, and that no man can with absolute certainty draw a stock tainted with the rot. There is another method, to which men of inferior skill resort, which is more easily acquired. They take a sheep's head between their hands, and press down the eyelids, they thereby make the sheep turn its eyeball so that they get a view of the vessels in which the eyeball rolls: if these are thin, red, and free of matter, they consider the sheep as sound; but if they are thick, of a dead white colour, and seem as if there was some white matter in them, they are confident she is rotten. This is a pretty general rule, and easily discerned; but I think it is not so certain as when they are judged by the back; for in firm healthy lands the eye of a sheep is far redder than it is in sheep upon grassy lands. And in some boggy lands the eye is never very red, be the sheep ever so sound, so that there you cannot so well judge by the eye; but when you see the eye of a sheep a good deal whiter and thicker, and more matter in it (I mean the vessels in which the eyeball rolls) than the run of the flock amongst which it feeds, you have reason to suspect it is not sound.
"There is another method by which I have seen some men attempt to judge of the soundness of sheep. It is a well known fact, that when sheep are rotten the lungs swell to a greater size; they therefore lay the sheep down upon its broad side, and pressing the skin in at the flank, up below the ribs,pretendto feel the lungs. But if there is anything to be learned by this I could never perceive it, and have seen some men, who pretended to know most by it, very often mistaken.
"These are the principal rules by which the Highland farmers draw their stocks; and they relate all to ewe stocks; for as to wedders, they are generally all sold off when they are three years old, and those that buy them for feeding mostly buy them by the condition they appear outwardly to be in at the time, and the character of the ground upon which they were bred."
(167.)Jaundice.I have never seen this disease in the sheep, and have heard almost nothing of it; indeed it is very rare, few having ever witnessed cases of it. It is consequently very imperfectly understood, every one who has written about it assigning for its occurrence a different cause. The principal symptoms to be depended on, according to those who have treated it, are a yellowness of the eyes, and an obstinate sluggishness of the animal, almost amounting to sleep. Copious bleeding and two ounce doses of Glauber salts have been recommended for the treatment, which must be gone about promptly, as the disease is said to be quickly fatal. Reasoning from what is known about jaundice in man, I would, were a case to occur to me in the sheep, give a good dose of calomel, say 15 grains, in conjunction with the salts, unless the disease had supervened on rot, when I would substitute ten grains of ipecacuanha for the mercury.
(168.)Dropsy.When it is the concluding symptom of a disease, it may be reckoned part of the complaint itself, and treated accordingly. Often, however, it is the first thing which attracts the attention of the shepherd, and when such is the case it will usually be traced to long exposure to cold and wet. In this event the best plan is to bleed largely, and give two or three smart doses of Epsom salts. When it occurs in young lambs, sweet spirit of nitre, given in the quantity of a tea-spoonful twice a-day, is found to be attended with the happiest effects. Tapping, or, as it is popularly termed,stabbing, orsticking, to permit the escape of the water, is the cure resorted to in South Africa, when it appears in old sheep, after exposure to rain; but this ought never to be resorted to unless under the guidance of a medical person. It would be much better at once to kill the sheep.
(169.)Sturdy.As shown in the tabular view of the diseases, in foot-note to paragraph (121), this affection may be the result either of pressure on the brain from an animal growth, or from the accumulation of a fluid. Serum is in both cases the mechanical cause of the symptoms, but in the former it is eliminated from neighbouring parts by a hydatid, while in the latter it is merely deposited in some of the natural cavities (the ventricles) of the brain, owing to a congested state of the spinal marrow, the result of continued cold upon the back.
Figure 2, Plate VII., taken from Rudolphi, exhibits a view of the animal which gives rise to the first variety of sturdy. It is the many-headed hydatid of the brain,Cœnurus Cerebralisof naturalists. Like theCysticercus tenuicollis, already described under the head of Rot, it consists of a thin membranous cyst, full or otherwise of serous fluid; but, unlike the aforementioned animal is studded over with groups of little velvety appendages or heads, each of which has a series of barbs projecting round the mouth. Figure 2,a, Plate VII., is a highly magnified representation of two of these heads.
A good idea of the hydatid, as it exists in the sheep, may be derived from an inspection of Fig 1. Pl. VIII., which has been engraved from a sketch kindly furnished to me by my friend Dr Kirk of Deal. Fig. 1 represents the brain of a sheep two years old, which has been affected with sturdy. The right lobe,a, of the cerebellum or lesser brain, is much distended with fluid, which is enclosed in a membraneous bag, as shown atb, where an incision has been made to expose it, and atc, where it is shining through one of the coverings of the brain, the pia mater.
The hydatid is found of all sizes, from that of a pea to that of Fig. 2, Plate VII. Large ones are far from rare, and the ventricle is frequently enormously distended. The hydatid in the brain from which Fig. 2, Plate VIII. was taken, though not filled to repletion, contained ten drachms of serum. The ventricle was consequently much dilated, as shown atain that figure, and the usual course and size of the convolutions completely altered. Instead of being folded, like the intestines, upon themselves, they proceeded, as seen atb b, from back to front of the brain; while the furrows between them, which are, in the healthy animal, usually too shallow to be measured, were in several places as deep as the length of the lines atc d.
This excessive accumulation of fluid within the brain leads, as might be expected, to the dilatation of the skull, and to the absorption of its walls, when the bones, young though the animal be when affected with sturdy, can no longer be made to yield. For this reason the skull, towards the termination of the disease, generally becomes thin and soft in front of the root of the horn, and in this way offers a spot which, from its being easily pierced, is frequently made the seat of surgical operations. Other parts of the skull also undergo considerable thinning, more so indeed than in front of the horn. The attention of the farmer has hardly, if ever, been called to this fact, though I believe that, for one instance in which perforation occurs in the frontal bone, it will be noticed a score of times on the sides of the head. In a head with which I was favoured by Mr Grieve, Branxholm braes, each temple, exactly beneath the superior extremity of the upright branch of the lower jaw, displayed a circular opening entirely through the bone, wide enough to permit the passage of an ounce bullet.
Whatever may produce pressure on the brain, the symptoms which indicate it are nearly always the same. The sheep has a dull, stupid look, turns very often round and round, and will, when water is in its way, stand staring at it till at last, giddy and confused, it plumps fairly in. If, when the symptoms are very unpromising, convulsive movements should occur, they may be taken as a favourable sign, as they indicate a diminution of the pressure on the brain. A minute description of the morbid appearances in hydrocephalus could serve no good purpose, I therefore pass on to the prevention of sturdy.
(170.)Treatment and Prevention of Sturdy.The variety caused by hydatids can only be prevented by the use of dry, well grown, wholesome food. Dr Jenner found that he could cause hydatids to form in rabbits at will, by feeding them on green succulent provision; and it is well known that this form of sturdy prevails among sheep chiefly in marshy places, as the fens of Lincolnshire.
Water in the head is generally induced, as first pointed out by the Ettrick Shepherd, in theFarmer's Magazinefor 1812, by the back of the animal being chilled, as is evident from the following facts:—