Chapter C: F. Dawson, in investigating a wasting disease of well fed Brahma (2)

_Hereditary Predisposition. Racial Vulnerability._ Before the discovery of the specific bacillus, when as yet tuberculosis was held to result from a constitutional weakness, or cachexia in which deterioration of cells was held to be the main factor, the disease was held to be mainly hereditary, and its every day transmission in the line of descent, and the increasing mortality to extinction of given families were confidently appealed to in support of the doctrine. Now, however, we recognize that congenital tuberculosis in man or beast is very exceptional, and that the morbid process almost invariably takes its start from the germ implanted after birth. In Saxony when the tuberculous cows were 16.5 per cent. tuberculous calves were but .2 per cent., though the latter had been fattened on the milk of the former. In Munich but two calves were found tuberculous in 400,000 killed, and in Lyons but five in a similar number. Up to the present the number of calves recorded as tuberculous at birth does not exceed seventy.

That the young almost always contracted the disease, only after birth, virtually disposes of the alleged heredity of the tuberculosis but it by no means antagonizes the heredity of the racial vulnerability. As man, cattle, swine and Guinea pigs show a much greater vulnerability than the carnivora in general, so certain families in each of these genera show a more decided susceptibility to tuberculosis under similar conditions than do certain other families. This goes far to explain the appearance of tuberculosis, in certain lines of blood, and its advance to the extinction of the family, while under no better environment, other families can count on a practical immunity. In the Burden herd of Jerseys in 1877, I condemned eleven animals, verifying my diagnosis by necropsies, and found to my surprise that I had taken every representative, even the grades, of a given family, and left all the pure bred members of a second family untouched. Both families had mingled freely in the pastures and yards, yet the second family furnished no cases of tuberculosis then nor for many years afterward. The case is all the more striking that the non-tuberculous family gave the largest yield of milk and might have been expected to run down rather than the other on account of this drain.

_Close Buildings. Lack of Ventilation._ Air rendered impure by being breathed again and again, predisposes strongly to tuberculosis, and has been even looked upon as the sole cause (Macormac). Everywhere city dairy cows, kept in confined, close buildings, suffer severely (6 to 20 per cent. and upward); in Berlin 75 per cent. (Ostertag); in Denmark 61 per cent. (Bang), while in the same districts country cows are comparatively immune (often 1 to 2 per cent.), and steers raised in the open air still less (0.02 per cent. for our Plains cattle). For the slighter cases of tuberculosis in man and beast, life in a pure open air, day and night, in a genial climate, gives the best hope of improvement or recovery. In the Burden Jersey herd above referred to, animals condemned in spring as tuberculous, were turned out to pasture during the summer where they maintained an appearance of robust health, yet when returned to the barns in fall they fell off rapidly, so that some had to be helped to rise in the stall. “The stabled cow, the tame rabbit, the monkey, the caged lion, tiger or elephant are almost invariably cut off by scrofulous affection” (Aitken). It has long been noticed that sailors sleeping in close spaces (Bryson, Parkes), soldiers confined to close stone barracks even in the tropics (Parkes), suffer much more than the officers in more spacious rooms (Clark). Monks and nuns (two-thirds of the deaths, Leudet) occupying confined cells, and the inmates of prisons (four times the average outside, Baer) have shown an extraordinary prevalence of tuberculosis and attendant mortality. While this can be attributed mainly to the preservation and concentration of the bacillus in such places, a considerable allowance must be made for the impure and rebreathed air.

_Dark, Foul, Damp Stables._ Dark stables are usually close, dirty and damp as well, and all these conditions alike conduce to tuberculosis. Darkness hinders the development of organic coloring matter in living bodies, whether chlorophyll in plants or hæmoglobin in the blood of animals. Hæmoglobin is the main oxygen carrier in the blood, and in case of its deficiency the tissues are not properly ærated. The result is as if the inhaled air contained little oxygen, so that darkness further intensifies the evil of rebreathed, deoxygenated air. The extraordinary mortality from tubercle among prisoners, monks, nuns and miners serves to further accentuate this conclusion.

Trudeau’s experiment with rabbits is instructive in this connection. Of a number inoculated with the same number of tubercle bacilli, one half were kept in the open air and the rest in a dark, damp, underground place deprived of sunlight. When killed on the same day, it was found that the open air rabbits showed only slight lesions or none, while the underground lot had extensive tuberculosis.

The impure stable air lowers the vital tone of the animal, especially if the impurity has come from animal exhalations.

The same is true of damp air, “a damp ship is an unhealthy one,” and Bowditch and Buchanan pointed out the especial prevalence of tubercle in cold, damp, undrained, foggy localities. This does not hold for all damp lands, yet damp, fog, and cold are especially hurtful in presence of the germ.

INSUFFICIENT OR UNWHOLESOME FOOD.

Starvation and indigestible or innutritious food contribute to debility, and lessen the power of resistance. Hence in the poor, half starved denizens of city slums, and among neglected herds of cattle, tuberculosis, once introduced, makes rapid and extensive ravages. Conversely overfeeding often acts in the same way, developing indigestion and thereby robbing the tissues of their proper nourishment.

HEAVY MILKING.

In dairy cows, of milking breeds, the drain on the system is liable to prove too great, under a ration-for-milk, warm sloppy mashes of grains, bran, middlings, roots, distillery swill, exclusive diet of silage, saccharine roots, or marc, warm drinking water, a warm atmosphere, liberal salting, and enforced idleness in the stall, with careful stripping of the bag. The butter cows, (Jerseys, Guernseys, Alderneys, etc.) are especially liable to suffer, as the greater the yield the more the system is robbed of the adipose material which is so needful to a vigorous health. When the cow has been reduced to a high-pressure milk factory her physical size reduced to obviate the need of a large sustaining ration, and her milking capacity stimulated to the highest degree, the presence of the tubercle bacillus is especially dangerous.

CONFORMATION.

It was formerly held that cows with heads narrow between the horns, small thin necks, narrow chests defective also in depth and length, loose projecting shoulders and elbows, pendent, pot bellies, with hollow flanks, and a general laxity of the frame were especially predisposed to tubercle. In many such cases the suspected animal was already the victim of the affection, which had brought out these characteristic features of weakness and emaciation. In other cases the unthrifty appearance was due to poor feeding and care or to chronic disease, which in robbing the system of vigor and hardihood laid it open to the attack of the tubercle bacillus whenever it was introduced. Even when there was no such depressing influence affecting the individual, the inheritance of such a frame, betokened a constitution lacking in vigor, and with little power of resistance to the invading microbe. Some milking breeds which tend to the above conformation, show an unusual development of the lymph glands and plexuses, and as tuberculosis attacks the lymphatic system preëminently, the bacillus finds an especially favorable field for development in such systems. It would, however, be an error to assume that the compact, rounded frame, with circular chest and abdomen, and full, firm neck and shoulders, with a great disposition to fat and little to milk, is in any degree immune. Under the presence of the tubercle bacillus, and close stabling, they often succumb quite as rapidly as the most susceptible milking breeds. The meat producing breeds with a strong propensity to fatten, have an extraordinary development of lymph spaces and plexus in the intermuscular and subcutaneous connective tissue, and the microbe finds a welcome home in their sluggish, inactive and atonic systems as well as in the typical dairy cows.

BREEDING TOO YOUNG.

Breeding from immature animals undermines the vitality as the system is overtaxed to sustain at once the demands for further growth, for the nourishment of the unborn offspring, and for the yield of milk. Some families of Jerseys have been undoubtedly injured in this way, through the desire to diminish the size of the cow, and yet retain the highest milk and butter yield.

CLOSE BREEDING.

Inbred families are proverbially subject to tuberculosis. By pairing individuals that show in a marked degree the desired qualities of early maturity, heavy milking, or fattening, the greatest stimulus is given to the enhancement of such qualities, and with this there is the correspondingly ready receptiveness to the tubercle bacillus. To this is added a degree of constitutional delicacy which comes from too close breeding, and which otherwise shows itself in an encreasing infertility, when bred with an animal that is nearly related. In addition, the high bred animal is kept much indoors, where the bacillus, once introduced, is easily preserved and propagated, and is denied the free outdoor life and exercise which might develop muscle and vigor. This is no valid argument for introducing inferior blood to the deterioration of the economic value of a race, but rather for the complete exclusion of the bacillus which may find in our treasured herd an especially inviting field for its ravages.

AGE.

In both man and beast, age appears to have a predisposing effect, but apart from debility or trauma, this may be fully explained on the ground of often repeated infection, an indoor life, and, in dairy cows, the excessive drain upon the system. In thoroughbred herds of cattle, in which the cows are preserved as long as they will breed, and in dairies where they are kept as long as the milk yield is satisfactory, the oldest show by far the largest percentage tuberculous. In secluded individual dairies we have found 100 per cent. affected, Ostertag gives the average for Berlin at 75 per cent., and Bang for Denmark at 69 per cent.

PREDISPONENT DISEASES.

As already noted all diseases which undermine the health tend to diminish the powers of resistance to the tubercle bacillus. To be especially dreaded, are long standing diseases which produce emaciation and debility, fevers that for a length of time impair sanguification, metabolism and nutrition, diseases of the digestive organs which cut off the requisite supply of nutritive material, and, above all, diseases of the lungs and air passages that impair the tone of the tissues and invite the attack of the invading microbe. Bronchitis, laryngitis, pharyngitis and tonsilitis in all their varied forms are to be particularly noted. Even in man it is believed that one of the most common channels of infection entrance is through the open tonsillar crypts, and the same doubtless is true of animals. Pigs, with their large tonsils and frequent infection through feeding, are probable examples of this, and when, in addition to the detention of the microbe in the cavities, there is an inflammation and debility of the tissues, the opportunity for infection is greatly enhanced.

ENCREASED TRAFFIC IN (TUBERCULOUS) ANIMALS. DAIRY EXTENSION.

In common with all infectious diseases, tuberculosis owes its great extensions to the sale and purchase of animals. Where an indigenous race of cattle is raised and sold, without any additions from without, tuberculosis is usually rare and confined to the one herd, or to those having intimate intercommunication with it. Where, on the other hand, a large stock is kept up, as in milk dairies, and few or no calves are raised, but the bulk of the cows are sold off yearly and replaced by new purchases, tuberculosis, sooner or later, finds admittance through the body of an infected animal, and once implanted in the herd, it goes on encreasing, without limitation, except by the sale or death of the more seriously affected. The larger the herd and the greater the number of yearly changes, the greater the number of opportunities for the introduction of an infecting animal. Where a great part of the herd is turned off yearly, and the new animals are drawn from any or every source indiscriminately, it would border on the miraculous if such a herd were to remain free from the infection for any great length of time. The recent extension of tuberculosis in herds has been coincident with the great development of commerce in live stock, and the rapid transit on land and water by steam. Before the days of the steam engine, animal plagues advanced slowly and uncertainly, excepting in the presence of a great European war, which drew animals from all available sources, congregating them in large mutually infecting droves in commisariat parks, and marching them in the wake of the army for its daily supply. Inevitably every country invaded was infected, and the plagues spread from the line of march in all directions. The more deadly plagues, like rinderpest and lung plague, were the first to appear, and in this lay a certain measure of palliation of the evil, as the exposed and often weaker animals were killed off, so that the slower contagion like that of tuberculosis had not time to develop. This mitigating influence held good so long as the deadly plagues were not placed under effective control. When, however, a nation successfully extirpated and excluded lung plague and rinderpest, the way was opened for a freer extension of tardily developing plagues like tuberculosis. The great development of beet sugar factories and the accumulation of herds to consume the marc; the extraordinary extension of manufactures which have made England and certain countries of Western Europe consuming rather than agricultural lands, and the wonderful modern expansion of dairy husbandry have combined to encrease and concentrate the cattle industry in ratio with the manufacturing and commercial progress of the nations, and as the live stock are kept under a milk-stimulating regimen and a life passed largely indoors, the way has been open for an ever-advancing encrease of tuberculosis. In the United States the centralization of population in the Eastern States and in all great centres of industry and the concentration of cows for the milk supply, and in certain districts in connection with butter and cheese factories, have contributed to wide local extensions of consumption. Hence it has been no uncommon thing to find herds in the vicinity of cities with 20 to 100 per cent. affected, in striking contrast with the 0.02 per cent. found in the fat cattle from the plains.

The modern railway traffic brings to all these swarming centres of animal industry, live cattle from long distances to supply the constant depletion through deaths and the disposal of dry cows, and thus the whole Atlantic slope is drawn upon to fill the eastern stalls. Infected animals thus shipped from Ohio, Indiana, Illinois, Wisconsin and Michigan for the good of the herds in those states find new homes in New York, or New England, where they have four to twelve mouths to propagate the infection before they are themselves disposed of. As in the days of the lung plague in America, the eastward trend of bovine traffic, becomes to a certain extent a protection and benefit to the herds of the west, but in equal ratio it operates to the detriment of our eastern stock. What is true of the planting of new centres of infection in the busy dairy districts of the east, and of the steady increase of disease in already infected herds, through the constant addition of new cases purchased, is no less true of the corresponding districts devoted to dairying interests in the west. It is the natural order of things, that, everywhere, the new accessions of infection, coming in the lines of trade, into large dairy herds, kept to a great extent indoors for months at a time, must hasten the general infection of such herds. When, therefore, no intelligent measures are interposed to check the evil, we must expect that the marked increase in the prevalence of tuberculosis, which we have witnessed of late years, shall become more and more evident year by year. Journals have claimed credit for befriending the stockman, in opposing all control of the cattle traffic, dealers have denounced all control as ruinously oppressive and injurious, and legislators have turned a deaf ear to the warnings of science and experience, but time, in this as in all other plagues, will justify the demand for an intelligent control, and the increasing losses will one day open the eyes of the stockowners to the fact that their truest friends are those that would exclude the baneful seed, and kill it ere it has had time to germinate and bring forth its ever increasing harvests.

In the absence of any systematic and efficient government protection in this line, the stock owner can only protect his sound herd by the rigid exclusion of all animals that are not of his own breeding, or in case of purchase, by an exhaustive inquiry as to the occurrence of sickness or deaths in the herd from which he buys, and by the professional examination and test of every animal to be bought. Even then he must promptly separate, test, and, if necessary destroy any animal that proves unthrifty, or which by cough, diarrhœa, wheezing or other sign gives evidence of probable tuberculosis.

_Unregulated Traffic in Tuberculous Animals from Other States._ The danger of buying animals untested is in no degree lessened when they are sent in from other states. While some make a business of supplying the store market with what they believe to be good stock, there is always the temptation to turn off animals that are unthrifty or poor milkers and which have proved less profitable than the others. Some even have the herd tested and sell off those that show evidence of tuberculosis. Unless, therefore, it is held in check by the tuberculin test, the traffic is made to the extent of such sales a direct means of disseminating tuberculosis.

ASSORTING THE TUBERCULOUS ANIMALS FOR SALE IN A GIVEN STATE.

A still more injurious result comes from the order of given States, that the admission of store cattle shall be guarded by the tuberculin test of each animal, and the supineness or worse, of adjacent states in establishing no effective safe guard against the disposal of the tuberculous culls in the unprotected State. Cattle from the west or elsewhere in the United States, arrive in a great public market as, for example, New York, they are here tested, those that stand the test are shipped into one of the States requiring the test (Massachusetts, Pennsylvania, New Jersey, Canada), and those that have shown the reaction of tuberculosis are sold into the herds of the State in which they were tested. The most malicious enemy of the New York stock owners, could not devise a surer means of stocking the herds of the State with tuberculosis than this atrocious system. Yet when the present writer had a bill introduced into the legislature to correct the evil the opposing interest proved strong enough to prevent it from coming to a vote. The legislative committee on tuberculosis which sat later, and upon whose attention the subject was pressed, also practically ignored it and the statute which this commission inspired leaves the matter as bad as before. Under the present law the New York purchaser must secure his own interests by having every animal he buys tested by a trustworthy veterinarian.

_Sale of Sound Animals Concentrates the Tuberculosis._ The action of one or more States in admitting store cattle only after a tuberculin test, acts directly in encreasing the relative number of tuberculous animals in adjacent States. The purchaser from Pennsylvania for instance, goes into a New York herd and purchases all the best animals on the condition that they pass the tuberculin test uncondemned. It follows that the New York herd is left with the tuberculous cattle only, and those that, aside from tuberculosis, are of low value or profitless to keep. Further as the advance of tuberculosis is proportionate to the relative number of tuberculous subjects in the herd or building, and the concentration of the poison, the depreciated herd is almost certain to become rapidly and generally affected by the disease.

_The Denial of Indemnity for Tuberculous Animals Killed._ Several American States (and notoriously New York in the recently enacted statute) forbid compensation to the owner for any animal killed because it is affected with a contagious disease, and to prevent the extension of such contagion. All history attests, and any consideration of human nature might teach, that such a measure is only calculated to spread the infection. The owner of an animal, affected with a contagious disease, who can get little salvage by turning it into beef, and none at all if he hands it over to the State for slaughter, will naturally think of putting it on the market, where he can secure a good price. How much more is he tempted to do this when the disease is an occult one, and the animal shows the outward appearance of health, as is the case in nine-tenths of many tuberculous herds! Crime cannot be fixed on the seller, for he is not an expert, and cannot be expected to diagnose the disease. If the infected cow is of little value for the dairy, she is passed on, from hand to hand, leaving infection in every herd she has entered. The ultimate owner (in whose hands the State finds her and diagnoses her disease), though he may have bought her in good faith as a sound animal and paid a correspondingly high market price, is made to lose the whole value of the cow. The real offender who knew her to be a tuberculous animal, and sold her in consequence at the price of a sound cow is shrewd enough to keep himself out of the clutches of the law, while the honest purchaser who has been already swindled, has his income and property cut off without compensation. Such a law is self-evidently unjust; it plays into the hands of the swindler at the expense of the just man; with the object of protecting the community against infection, it refuses to call on the public for any contribution toward its own protection. The system is a direct bid for extensive and encreasing violation of the law and diffusion of the infection and must be accorded a prominent place in the list of causes. It would be surprising to find that any country ever extirpated an animal plague by working on such a system. As a matter of fact no country ever did; all such sanitary successes from the extinction of sheeppox or rinderpest in Western Europe, to the recent _stamping out_ of lung plague in the United States, were based on a just compensation to the owners of the stock. When, therefore, veterinary sanitary principles and experience have been so far ignored as to allow the passage of a law, which at once favors the diffusion of infection by the crafty sale of the infected, the expatriation of the healthy animals from the home herds, leaving only the diseased, and finally the selection from herds in transit of the tuberculous ones to be scattered widely among the herds of the State, we must not wonder at the continuance or encrease of tuberculosis in the commonwealth. Until a more rational and common sense legislation can be secured, the unfortunate stock owner must defend himself by the expensive alternative of testing every animal he buys.

_Private Testing of Herds and Sale of the Tuberculous._ A most reprehensible practice is the private testing of herds and the sale as store animals of those that react. In this way a herd may be cleared of infection, but at tenfold expense to the public at large, as every animal sold may convey the infection into a separate herd. It is, however, a natural outcome of the unwise system of refusing indemnity for the infected.

_Habituating to Tuberculin Testing and then Selling under Test._ Many (not all) cattle, when injected with tuberculin repeatedly at short intervals, acquire a tolerance of the agent and fail to react as at the first test. We have in such cases examined the animals _post mortem_ and found active tuberculosis. Unscrupulous owners, aware of the fact, have their diseased cattle injected repeatedly every few weeks, and as soon as they fail to respond, sell them under the guarantee of the tuberculin test. The cattle, of course, carry the infection into other herds. This swindle could be obviated if it could be made a misdemeanor to have or use tuberculin except as a State or Federal official acting for the government. This would imply the corollary that the State should test the herds when called upon.

_Antipyretics During Tuberculin Test._ Another method of undoing the tuberculin test is to feed large doses of antithermic agents to depress the temperature at the time the rise from tuberculin would take place. Tuberculous cattle may thus be sold as sound animals, with a certificate of having successfully passed the tuberculin test, the operator having given such certificate in perfect good faith. It suggests the importance of withholding tuberculin from public use, or of securing an absolute control of the feeding and watering of the animals during the test.

_False Certificates of Tuberculin Tests._ Stock owners have reported to the writer alleged tuberculin tests of their herds which were completed in three hours, and others have named instances of marking animals for shipment and giving certificates of testing where no tuberculin had been used and no examination beyond the most cursory glance had been made. This might be expected of some non-graduates, registered on a basis of alleged practice, shamefully ignorant of veterinary medicine and conscious of their false position, and some educated veterinarians thus placed at a disadvantage may have been tempted to follow suit, but it can only end in personal disgrace and an inevitable extension of tuberculosis. Begotten in a legislative wrong and nourished by moral weakness, it can only grow into greater evil. Unfortunately such unworthy actions throw discredit on the very name of sanitary police. To avoid the evil every one aspiring to the responsible work of testing cattle should be thoroughly examined as to fitness and licensed to practice under a heavy penalty for neglect or malpractice.

_Feeding Hogs on Fresh Offal from Abattoirs._ It has been a common practice, especially in country districts, to turn the raw offal of slaughterhouses to pigs, and as the tubercle is usually concentrated in internal organs, the hogs become infected in large numbers. In public institutions which slaughtered their own meat I have found the hogs all but universally tuberculous. The danger is only slightly lessened when the hogs are fed raw butcher and kitchen scraps in swill. It suggests the compulsory boiling of all swill or garbage containing raw meat.

_Feeding Calves and Hogs on infected Milk._ Though it has been repeatedly shown that the majority of moderately tuberculous cows do not yield infected milk, yet in every tuberculous herd, at irregular intervals, one or more are attacked with tuberculosis of the mammæ, and the drinkers of the milk take in the tubercle bacilli. This will happen in the most strictly supervised tuberculous herds, while in those that are less carefully managed, the milk that is considered unfit for human consumption is fed to pigs or calves. In one dairy, I found that the calves, all fed in this way afterward reacted under the tuberculin test, while the following year the crop of calves, though fed on the milk of the same diseased cows, with this difference that the milk had been first heated to 180° F., without exception grew up healthy, and not one reacted under the tuberculin test.

_Feeding hogs after Tuberculous Cattle._ Where cattle and hogs are kept on the same place, it is a common practice to let the swine clean up all food left by the satiated cattle. If there are tuberculous cattle, affected either in the air passages or alimentary tract, the pigs become infected by taking in the expectoration by which the food is soiled, or by rooting around where the cow manure has fallen.

_Feeding from a Common Trough._ In an infected herd, a common cause of extension is found in the use by the whole herd of a common feeding trough, in which the food soiled by virulent discharges, is taken by healthy animals. The habit of tying a cow in different stalls in succession as she happens to strike one, in place of keeping each cow by its own stall is a fruitful source of infection. Even when each cow is kept by its own stall, she often becomes infected by reaching into the feeding trough in front of the next cow on the left or right and taking in soiled and infected fodder. In swill stables the evil reaches its maximum, as the feeding trough for 50 or 60 animals is slightly inclined so that the liquid food runs from the supply end to the other, and infecting expectorations are carried in front of all in turn.

_Dry, Dusty Stables._ Tubercle bacilli are not carried out on the expired air, unless there is forced expulsion as in coughing, snorting or sniffing. In such cases the solid particles are thrown off in masses or fine spray and lodged on surrounding objects. These, together with infecting discharges from bowels, urinary or generative organs, open sores, etc., dry up, and rise on the dust, and, as sterilization occurs slowly indoors, they cause more or less infection of the animal inmates. Cornet, Tappenier and others have thoroughly established this as a common form of transmission, and shown the great importance of cleanliness, disinfection and the removal of infecting materials without raising dust. In an establishment in Paris, a consumptive had served for 3 years. In the following 10 years, 15 of the 20 employés died of phthisis.

_Extension through Vermin._ As rats and mice (and other rodents) are susceptible to tuberculosis by ingestion (Galtier) it follows that they may become the media for extension of the infection through fodder in which their droppings are scattered, or from their feeding in the same troughs as the cattle or swine. For swine in particular the danger is greater because of their carnivorous habits; the rat acquires tuberculosis through eating the offal of the abattoir, or the scraps of the butcher’s stall, or kitchen, and the sick rat is thereafter easily caught and devoured by the pig to its own undoing. To block this channel of infection the destruction of vermin about slaughter houses, stables and pig pens is a most important consideration.

_Flies and Other Insects as Carriers of Tuberculosis._ These congregating on tubercular sores, around the nares or lips, on the skin contaminated by the virulent bowel discharges, on dishes holding infecting milk, on objects soiled by infecting discharges, on diseased carcasses at abattoirs, rendering works and elsewhere, (Spillman, Hoffmann, Lartigan, etc.,) and on graves where the earth worms have brought the bacillus to the surface, (Lortet, etc.) become more or less active agents in disseminating the virus. In this way food and water are contaminated, and exceptionally, infection may even be implanted on sores. As the excreta of the flies contain the virulent bacilli, the latter are deposited on windows, walls, furniture, etc., and may be later disseminated in the dust of the apartment.

Dewevre found tubercle bacilli in the bedbugs infesting a bed in which successive cases of consumption had developed, showing that other parasitic or rapacious insects besides flies must be looked on as possible propagators of the bacilli. There is reason to suspect, lice, fleas, ticks and acari especially. The same is true of leeches and other rapacious invertebrates.

LESIONS. THE TUBERCLE.

The characteristic lesion in tuberculosis is the tubercle, taking its name from the small rounded nodule which, at first virtually invisible, encreases often to the size of a millet seed, or a pinhead or even larger, and which by confluence with others, forms conglomerate masses of all sizes to which the term tubercle is still applied. Where the bacillus tuberculosis is implanted, the fixed tissue cells are stimulated to an undue proliferation, and a diapedesis of leucocytes takes place from the neighboring capillary blood vessels, the whole eventuating in the formation of a rounded cluster or nest of epithelioid and giant and later small rounded lymphoid cells in a fine fibrous stroma. Baumgarten and his followers claim that the larger epithelioid and giant cells result from the karyokinesis and proliferation of the fixed tissue cells, epithelial and endothelial cells, and that the lymphoid cells which later (often after the eighth day in experimental cases) invade the lesions, are alone the product of the migrating leucocytes. Metchnikoff, Yersin and others contend, on the other hand, that epithelioid and giant cells are directly derived from the leucocytes and endothelial cells and like these are possessed of actively phagocytic qualities. As the final outcome before caseous degeneration, is the great predominance of the small lymphoid cell, it may well be questioned whether this is not the result of active encrease in both kinds of cells, as appears to happen in many other inflammations. For our present purpose it is well to note the early characters: _Centrally_ often a large (giant) cell with a number of peripheral nuclei and at times, branching processes; around this as a _second zone_ epithelioid cells of large size, with round or oval nuclei, and sometimes giant cells; outside this a _third zone_ of small rounded lymphoid cells with large nuclei. There is a delicate fibrous network between the cells, but no indication of capillary blood vessels, the absence of which may partly explain the constant tendency to degeneration, necrosis, and caseation. The tissue around the miliary tubercle is red and congested.

_Caseation._ A striking characteristic of tubercle is the occurrence of coagulation necrosis, beginning in the centre of the specific nodule as a whitish or pale softening and degeneration of the cell elements and gradually extending toward the circumference. The cells, and even the proximate tissue elements, die and disintegrate passing into a structureless, granular or hyaline debris, which has been named from its supposed resemblance to old, ripe, soft cheese. Baumgarten has observed that the small lymphoid cells are the first to degenerate, followed by the epithelioid and giant ones.

While the formation of tubercle is at first a productive inflammation of which the cell clusters and nodules are the result, yet the tendency to necrosis, and caseation is so great that it must be looked upon as one of its most prominent features, and is rarely absent, whether the lesion exists in the connective tissue of the lungs, liver or other organ, in the lymph glands, in the respiratory or intestinal mucosa or submucosa, in the osseous cancelli, brain or skin. It is, therefore, largely pathognomonic, yet it is not peculiar to tubercle, being common in glanders, and other infective inflammations. Its presence should always lead to a search for the primary tubercle nodule, with its nonvascular cluster of lymphoid and giant cells and above all for the specific bacillus resistant to staining.

The tendency to extensive degeneration and caseation is especially marked in swine, in which the resulting debris is often so liquid that the tubercles bear a strong resemblance to abscesses.

_Calcification._ The deposition of lime salts (mainly phosphates) in the tubercle is a common feature of advanced cases in man and pig, but especially in cattle. It is unknown in rabbits and Guinea pigs. The tubercle assumes a hard cretaceous aspect and feeling, grates under the knife and crepitates when pressed. This is always an evidence of chronicity, but it has been observed in swine in 3½ months.

_Fibroid Degeneration. Fibrosis._ In this case a productive fibroid inflammation takes place in the tissue of the tubercle, and it is resolved more or less extensively into a hard, white, resistant body. This is the pearly mass which has given rise to the name of the _pearl disease_ (perl-zucht) in Germany. It may be fibrous throughout, but usually a number of the nodules show a caseated centre while the external zone, that nearest to healthy tissue, has alone taken on the conservative fibroid development. Like cretifaction, fibrosis is an indication of chronicity in the lesion. It is often seen in man, but still more so in cattle, in which it affects particularly the abdominal cavity, but also to a lesser extent the chest and other parts. It is remarkable for the paucity of bacilli to be found in its substance, often requiring many sections and infinite patience to reveal the presence of the microbe. This comparative lack of actively multiplying bacilli is doubtless one factor, operating in the direction of conservative processes, chronicity and even partial recovery. In experimental tuberculosis the extent and rapidity of development of tubercle, as also of the degeneration are found to be closely allied to the number of bacilli introduced.

_Cattle: Pulmonary Tuberculosis._ One of the most frequent seats of tuberculosis, the lung, may in acute cases show a diffuse miliary tuberculosis, a considerable part of a lobe or of several lobes being congested, infiltrated, and filled with small individual tubercles, grayish or transparent in the midst of the general redness. A second form, often of old standing, is in the shape of hard masses, often circumscribed or isolated, and easily felt when the soft lung tissue is manipulated. They are respectively formed by the local aggregation, and confluence of the small miliary nodules and may vary in size from a pea to a mass of ten or twelve inches in diameter. On section the miliary tubercle may not yet show central caseation, but the larger ones do so as a rule. The caseated nucleus may be soft, cheesy and somewhat homogeneous; it may be dry, granular and yellow, resembling damp farina of maize; it may be calcified in its outer portion and invested by a firm fibrous envelope. The tubercle may be the seat of general fibroid degeneration, constituting the pearl nodules (perl-knoten) dense as cartilage and either with or without a soft caseated centre; it may show an agglomeration of nodules in all stages from the early congested nodule to advanced caseation or cretefaction, the whole embedded in a solid congested and infiltrated tissue, largely fibroid. There may be extensive abscesses, the seats of complex infections, having thick uneven walls, often showing _grape like_ tuberculous outgrowths, and containing thick, caseopurulent, viscous, granular, yellowish or greenish and comparatively odorless contents; in other cases the abscesses have burst into the bronchia, leaving _vomicæ_ and with the new resultant infections the contents have acquired an offensive putrid odor; finally, there may be extensive inflammatory infiltrations, affecting lobules or lobes, and interspersed with tubercles in the form of the early grayish or transparent nodule, or even more advanced caseous or cretaceous centres. These latter serve to distinguish the condition from broncho-pneumonia, the grayish centres of which might suggest miliary tubercle. The broncho-pneumonia, however, has the whitish centres confined to the bronchioles and their terminal air sacs, and represent their thickened walls and muco-fibrinous contents; they do not show the same tendency to caseation, nor necrosis of the tissue, nor to caseation of the dependent lymph glands, and, above all, they do not contain the bacillus tuberculosis.

A noticeable feature in the tuberculous lung is the great frequency of tubercles of all different ages from the initial transparent nodule to the caseated or calcified mass side by side. A tuberculous bronchitis is a familiar accompaniment, with lines of miliary tubercles, ulcers and a flocculent (sometimes gritty) muco-purulent discharge, containing elements of the necrotic tissue and bacilli. Emphysema and interlobular œdema are also met with.

The _Pleuræ_ often suffer by continuity of tissue from the diseased lung, but they may be affected primarily through infection of the circulating blood. The earliest pleural lesions may be congestion, exudation and the formation of false membranes in fringes, but soon these become the seats of minute nodules or forming tubercles which steadily encrease to form pale red cauliflower-like growths—which have been spoken of as _grapes_, from their supposed resemblance to bunches of that fruit. Extensive areas of the mediastinal, costal or pulmonic pleuræ are often completely covered by these productions. Dense, and thick adhesions sometimes form, holding in their substance characteristic tubercles.

The _bronchial and mediastinal lymph glands_ receiving as they do the afferent trunks from the lungs and the great lymph sac of the pleura, offer in their sluggish currents the most favorable culture vessels, and almost always become affected in consequence. Not unfrequently they are found to be tuberculous when the tissues which they drain appear to be sound, and we must therefore, conclude that the primary slight lesions in the latter have recovered, or that the bacilli have passed through the tissues and lymph channels without establishing any centre of disease. The glandular lesions are primarily congestion and redness, with more or less infiltration and swelling, followed by a nodular induration, with enlargement or exceptionally shrinking. When bisected they may show all stages of the tubercle from the miliary granule to the caseous, dry, yellow, granular or cretaceous necrosis. By aggregation these often grow to a large size, a long diameter of 6 to 12 inches being not uncommon.

_Pericardial and Cardiac Lesions._ The pericardium may be implicated from the pleuræ or independently, and though tuberculosis of the heart is rare, it may be the seat of primary tuberculosis or of extension from the pericardium or endocardium. In the N. Y. State Veterinary College Museum is a cow’s heart, greatly enlarged, and completely invested and invaded by tubercle several inches thick.

_Tuberculosis of the Mouth and Throat._ Tubercles sometimes form in the _tongue_ causing nodular swelling, with a caseated centre. Much more frequently they attack the _pharynx_ or _larynx_ with the formation of nodular necrotic swellings, followed by ulcers and the implication of the adjacent lymph glands. The glands are liable to be invaded through the tonsillar and other follicles of the faucial and pharyngeal regions, which like the solitary and agminated glands of the intestines form excellent culture vessels. The glands most frequently attacked are the _retro-pharyngeal_, but the _lateral pharyngeal_, the _intra-parotidean_ and _submaxillary_ lymph glands occasionally suffer. They often become indurated, yet the formation of abscess-like sacs is not uncommon especially in the retro-pharyngeal.

_Gastro-Intestinal_, _Peritoneal_ and _Mesenteric Tubercles_. Tubercles of the interior of the stomachs are rare, though they are frequent on the peritoneal surface of the first three stomachs, as rounded, subserous nodules varying in size from a pea upward. The _mucosa of the small and large intestines_ may suffer, by preference in the seats of the solitary or agminated glands, and the resulting ulcers may extend in the lines of the lymph vessels from the convex to the attached border of the gut. The small greenish caseated and calcified nodules on the intestines, which are so often mistaken for tubercles, are the degenerated cysts of the œsophagastoma. Tuberculosis of the mesenteric lymph glands is much more common, the successive stages being essentially like that seen in the bronchial glands. Beside these the surface of the mesentery, omentum and abdominal parietes often becomes the seat of congestion, exudation and cauliflower-like neoplasms or grapes, as already stated of the pleuræ. In a certain number caseation or cretefaction may be detected.

_Liver Tuberculosis._ The liver is greatly exposed to tuberculosis as the single destination of all the blood from the gastro-intestinal tract. Tubercles also form on its surface by direct infection from the peritoneum. The hepatic tubercles are often very large and numerous, adding greatly to the bulk and weight of the viscus. There is usually coincident tuberculosis of the lymph glands of the porta.

_Tubercle of the Spleen._ This is also a favorite seat of the morbid process, exposed as it is to the reflux of infected blood in the portal vein, and to access of the bacillus from the peritoneum and omental lymphatics.

The _pancreas_ is less exposed to the channels of the circulation and is less frequently affected.

_Genito-Urinary Tubercles._ The _kidneys_ are always liable to suffer in generalized tuberculosis, in accordance with their function of elimination and the great quantity of blood that passes through them. The tubercles may be numerous, encroaching upon and destroying the glandular tissue, and determining congestion, nephritis and hæmorrhage (Schütz). The _ovaries_, when tuberculous, lead to nymphomania and sterility; they become swollen, with rounded projections, indurated, and on section show all stages of infiltration, caseation and calcification. They may encrease to a great size. Tubercles are found on the _Fallopian tubes_, the _serous and mucous surfaces of the womb_, and in the _broad ligaments_, in all their characteristic forms. The _bladder_ and _vagina_ are less frequently involved. In the male the _testicle_, _epididymus_, _tunica vaginalis_ and _prostate vesicles_ are sometimes affected. The swelling and induration of the affected organ, or the existence of hydrocele, may be noted.

_Tubercle of the Udder._ From the mass of blood passed through the udder it is specially exposed to infection whenever the bacilli enter the circulation. It may also be directly infected by the entrance through the teat, or a trauma, of the bacillus of the stable dust. There may be for a time only a slight general swelling which leads to no suspicion on the part of the milker, and as the secretion is not arrested, a dangerous product may be distributed. At this stage the lobules on section appear swollen, gray, with paler or yellowish points and minute hæmorrhages. The milk ducts contain coagula and bacilli (Bang). In other cases, usually more advanced, the gland is hard, nodular, enlarged, and shows a marked thickening of the walls of the smaller milk ducts and secreting follicles, with yellowish and even caseous and calcified centres. The gland is often greatly enlarged, the milk suppressed or completely altered, and tubercular neoplasms or ulcers exist in the larger ducts.

_Tuberculosis of the Brain and Spinal Cord._ As noted in Volume III. this occurs in young cattle especially in the form of tubercles of all ages attached to the pia or arachnoid, on the brain, or cerebellum, or in the ventricles, also in the cerebral matter, in or on the lumbar enlargement of the cord or on its pia. Several cases have come under my notice in the mature cow.

_Tuberculosis of the Eye._ This has been seen mainly as a result of experimental inoculation, yet casual cases also occur in the cornea, sclerotic, iris or choroid, the product undergoing early necrosis and softening into a yellow mass filling the different chambers.

_Tuberculosis of the Bones._ Though less frequent than that of internal organs this is not rare. It usually attacks the spongy tissue, near the articular extremities, or the vascular line between epiphysis and diaphysis, giving rise to considerable exudate, thickening of the bone and arthritis. The vertebræ, ribs, sternum, petrous temporal, frontal and occipital also suffer. Sections of the bone show dilatations of the cancelli, filled with the characteristic nonvascular groups of giant, epithelioid and lymphoid cells with, at times, softened and caseated centres. The adjacent bone is congested and softened, so that the detachment of epiphysis and apophyses is not uncommon. In case of invasion of the joints the cartilages and ligaments are the seat of tubercular deposits, softening, fibroid change and caseation, and there is general synovitis. The cartilages of the ear (concha) and nose (septum) may also be invaded.

_Tubercles of the Skin._ These are not very uncommon in cattle being the counterpart of the tuberculous warts and ulcers of the hands of butchers, tanners and others that handle the products of diseased animals. They may show as little pea-like nodules in the substance of the skin, or immediately beneath, very commonly on the side of the abdomen, where their presence in life furnishes a useful suggestion, as enlarged masses forming raw, warty projections with centres of caseation, or as clusters of warty-like growths of this kind (grapes).

_Tuberculosis of the Muscles._ This is comparatively rare in cattle, though by no means unknown, appearing as tubercles of the size of a pea and upward, in or between the muscular masses, often showing a caseated centre.

_Tubercle of Lymph Glands._ No organs in the body suffer more than the lymph glands as they receive through their afferent trunks and develop the bacilli coming from any adjacent tissue to which they are subsidiary. There is also evidence to show that bacilli entering from the lungs or bowels may pass through these without apparent effect to develop in the connected lymph glands. The frequent infection of the pharyngeal, bronchial, mediastinal and mesenteric lymph glands has been already sufficiently noticed, and if the other groups suffer less it is mainly because the tissues from which they derive their lymph are less frequently infected. An intimate knowledge of the different groups of lymph glands is a most essential prerequisite to the diagnosis of tuberculosis in life, and no less to a satisfactory _post mortem_ examination. The order of relative susceptibility and importance is somewhat as follows: Bronchial, mediastinal, mesenteric, hepatic, sublumbar, mammary inguinal, subdorsal, phrenic, intercostal (especially the first and second), pharyngeal, parotid, submaxillary, prescapular, prefemoral (stifle), prepectoral, axillary, cubital and popliteal.

_Relative Frequency of Tubercle in Different Parts in Cattle._ The following table gives the seat of tubercle as noted by a number of observers. It is open to the objection that it is the result of examination for diagnosis, and therefore gives the most obvious rather than the complete list of lesions. Examination of the brain, bones, deep muscles and intermuscular glands, etc., was usually omitted. Again, as the animals were often steers, the indications as regards the generative organs are unreliable. The œsophagostoma nodules on the bowels have been so often mistaken for tubercles that I have omitted all reference to intestinal tubercle.

DISTRIBUTION OF TUBERCLES IN DIFFERENT ORGANS OF CATTLE: PER CENT OF
AFFECTED CATTLE.

────────────┬─────┬───────────┬────────┬──────────┬──────┬───────
│ % │ │ │ │ │
│Right│ % │% Costal│ │ │
│Lung.│Mediastinal│Pleura. │ │ │
│ % │ Glands. │ % │ % │ │
│Left │% Bronchial│Visceral│Mesenteric│ % │ %
│Lung.│ Glands. │Pleura. │ Glands. │Liver.│Spleen.
────────────┼─────┼───────────┼────────┼──────────┼──────┼───────
German │ │ │ │ │ │
Abattoirs,│ 75 │ 29 │ 47–55 │ │ 28 │ 19
Pearson, │ │ │ │ │ │
(Penna), │63–57│ 60.7–33.8 │ 22 │ 23.25 │ 20.7 │ 5.7
Bryce │ │ │ │ │ │
(Canada), │77.27│ 56.8 │ 11.36 │ 11.36 │ 40.9 │
Reynolds │ │ │ │ │ │
(Minn. │ │ │ │ │ │
Agr. Ex. │ │ │ │ │ │
Station), │89.4 │ 33.3–64.9 │ 79 │ 12.5 │ 35.4 │ 27
Law (N.Y. │ │ │ │ │ │
Grade │ │ │ │ │ │
Herds), │34.8 │ 64 │ 6.4 │ 9.6 │ 1.6 │
Nelson (N. │ │ │ │ │ │
J. Exp. │ │ │ │ │ │
Station │ │ │ │ │ │
Cows), │33.9 │ │ │ │ 28 │
Russell │ │ │ │ │ │
(Wis. Exp.│ │ │ │ │ │
Station), │ 55 │ 72.4 │ │ 24 │ 10 │
Stalker & │ │ │ │ │ │
Niles (Ia.│ │ │ │ │ │
Exp. │ │ │ │ │ │
Sta.), │ 36 │ 61 │ │ │ 8.3 │
Reick │ │ │ │ │ │
(Leipsic),│ 100 │ │ [2]57 │ │ 83 │ 18
────────────┴─────┴───────────┴────────┴──────────┴──────┴───────

────────────┬───────┬───────┬───────┬───────────┬──────────┬──────────
│ │ │ │ │ │
│ │ │ │ │ │
│ │ │ │ │ │
│ │ % │% Liver│ │ % │
│ % │Lumbar │ Lymph │ % │Pharyngeal│ %
│Uterus.│Glands.│Glands.│Peritoneum.│ Glands. │Diaphragm.
────────────┼───────┼───────┼───────┼───────────┼──────────┼──────────
German │ │ │ │ │ │
Abattoirs,│ 10 │ 5 │ 1 │ │ 4 │ 0.2
Pearson, │ │ │ │ │ │
(Penna), │ 5.5 │ │ 10.3 │ 14 │ 15.15 │ 11.4
Bryce │ │ │ │ │ │
(Canada), │ │ │ │ 45 │ │ 2.27
Reynolds │ │ │ │ │ │
(Minn. │ │ │ │ │ │
Agr. Ex. │ │ │ │ │ │
Station), │ │ │ 8.3 │ │ 18.7 │
Law (N.Y. │ │ │ │ │ │
Grade │ │ │ │ │ │
Herds), │ │ │ │ 17.7 │ 6.4 │
Nelson (N. │ │ │ │ │ │
J. Exp. │ │ │ │ │ │
Station │ │ │ │ │ │
Cows), │ │ │ │ │ │
Russell │ │ │ │ │ │
(Wis. Exp.│ │ │ │ │ │
Station), │ │ │ │ │ 31 │
Stalker & │ │ │ │ │ │
Niles (Ia.│ │ │ │ │ │
Exp. │ │ │ │ │ │
Sta.), │ │ │ │ │ 5 │
Reick │ │ │ │ │ │
(Leipsic),│ │ │ │ [2]57 │ │
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