TUBERCULOSIS INVESTIGATIONS.

The most important investigations made during the past year concern the disease known as tuberculosis. An experiment to determine the value of the method of immunizing cattle against tuberculosis, developed by Pearson in the United States and by Von Behring in Europe, is nearing completion. In a general way our work has shown that this method of immunization actually protects cattle fairly well against tuberculosis, but as it requires the introduction into their tissues of living tubercle bacilli of the morphologic type more commonly associated with the tuberculous lesions of persons, it is questionable whether its extensive practice should be advocated. This is especially true in the light of the work reported by various investigators relative to the elimination of tubercle bacilli from the bodies of cattle after injection in various ways. It is claimed by some of these investigators, for example, that tubercle bacilli injected under the skin or into the circulation of a cow are to some extent eliminated through the udder with milk. If this claim is true, no system to protect cattle against tuberculosis that requires the introduction of living tubercle bacilli into their bodies can be characterized as anything better than a means to protect live stock at danger to public health.

Another method of immunization against tuberculosis is also being tested. This is known, named after its inventor, as the Heymans method. It is simply the introduction of virulent tubercle bacilli, enveloped in a sack of vegetable fiber, which in turn is inclosed in a gelatin capsule, under the skin of the animal. It is too early to say much about this method, though some of our observations tend to discourage great expectations either as to safety or efficiency. The Heymans capsules are claimed by their inventor to confine tubercle bacilli so that they can not actually pass into the tissues of a treated animal. Anthrax bacilli, which are much larger than tubercle germs, introduced into Heymans capsules under the skin of sheep, have been found to pass rapidly through the walls of the capsules and cause fatal disease accompanied by the usual presence of innumerable anthrax bacilli in the blood.

Considerable attention was given to hog tuberculosis, with special reference to the sources from which the bacilli that cause it are more commonly derived. More work is necessary before a complete report can be written on this subject, but it is interesting to know that among three lots of hogs exposed respectively to milk from tuberculous cows, feces from tuberculous cows, and to hogs affected with tuberculosis, those exposed to feces contracted tuberculosis much more frequently than the other lots. This bears out our former conclusion that the feces of tuberculous cows are probably the commonest cause for the propagation of tuberculosis among hogs. As far as our work has gone the exposure of hogs to the feces of tuberculous cows has infected them with fully ten times the certainty that followed their exposure to tuberculous hogs or from feeding them the whole milk of tuberculous cows. Examinations made by the Bureau have shown, however, that tubercle bacilli are present in a very large percentage of the samples of centrifuge slime from public creameries. In view of the danger from these two sources hog breeders are urged to protect their hogs from contact with the feces of cows that have not been proven by the tuberculin test to be free from tuberculosis, and

to boil the skim milk which is obtained from public creameries and used as hog feed. It is gratifying that the work of the Experiment Station demonstrating that apparently healthy but tuberculous cattle intermittently expel tubercle bacilli with their feces now has the confirmation of the British Royal Commission on Human and Animal Tuberculosis (see Third Interim Report of the Commission, issued at London early in 1909).

During the year an article that pronounced tuberculosis in all its forms to be a bacteriemia, and that received unusually wide attention, was published by an American investigator. As this view, which stamps the disease as being constantly associated with the presence of numerous tubercle bacilli in the blood, had an important bearing on the meat-inspection regulations of the Bureau with regard to tuberculosis, an investigation was immediately undertaken to prove definitely to what extent the blood of tuberculous subjects actually contains tubercle bacilli. Numerous microscopic examinations and inoculation tests were made with the blood of tuberculous cattle. Some of the cattle were long-standing cases of generalized tuberculosis and were expelling numerous tubercle bacilli in their feces. In no instance were tubercle bacilli found in the blood, and hence we are justified in concluding that, in animals at least, tuberculosis is not a disease that can be characterized as a bacteriemia in any sense of the word, though in some forms of tuberculosis the bacilli may in rare instances be present in the blood, probably for short periods of time.

A number of tuberculous cattle were kept at the Station to test the potency of the tuberculin sold by different manufacturers in this country. The tuberculins tested during the year were all found to be satisfactory.

It is of some importance to record in connection with the various tuberculous cattle kept under close observation at the Station that the frequency with which udder tuberculosis developed among them is surprising. The development of the disease in the udder in one or two instances was so insidious that the milk of the cows was found to be infected with tubercle bacilli by guinea-pig injections long before the slightest lesion of local disease could be detected by a physical examination. In one instance it was determined, after weeks of inoculation tests, that infected milk was produced by one quarter of the udder of a seemingly healthy but actually tuberculous cow, while the remaining three quarters produced noninfected milk.

One case of udder tuberculosis observed in a cow is particularly instructive. The disease extended to and developed in the udder with great suddenness and violence. In the course of a few days an apparently healthy udder, including the associated lymph glands, became affected with a diffuse tuberculosis that wholly destroyed its normal function. Half of the udder became so swollen that its size was at least three times as great as normal. On post-mortem examination no real typical lesions of tuberculosis could be found, but the entire affected region was saturated with unusually virulent tubercle germs. This case shows how great the danger may be from a tuberculous cow, even when it can not be proven that her milk contains tubercle bacilli, and that tuberculosis of the udder may develop without warning at any time in a tuberculous cow.

An investigation has been planned to determine whether the use of pasteurized milk containing dead tubercle bacilli is injurious to the

health of those who drink it, either because the dead bacilli may cause pathological conditions or because swallowing dead tubercle bacilli may lower the normal resistance of the body to living tubercle bacilli, a few of which, under existing conditions, are almost certain to find their way, sooner or later, into the body.

An investigation is also in progress relative to the percentage of healthy calves that can be raised from a herd of tuberculous cattle. The object of this investigation is to obtain additional and muchneeded data regarding the economic eradication of tuberculosis from among cattle. This investigation is also of special interest because it may throw some light on the possible development of tuberculosis during later stages of life from tubercle bacilli that were swallowed during the true milk-drinking period.

RABIES.

During the year a number of dogs that had been bitten by rabid dogs were kept in quarantine, and one horse that had been bitten by a rabid dog was treated under the direction of, and with material received from, the Hygienic Laboratory of the United States Public Health and Marine-Hospital Service. The horse was discharged in perfect health ninety days after the treatment was completed, and as nothing has since been heard from the case the treatment was undoubtedly effective in preventing the development of rabies.

If the frequency with which the attention of the Station has been called to rabid dogs has any value as a guide to the prevalence of the disease, we may conclude that it is still markedly in evidence in and about the District of Columbia.

OTHER DISEASES.

Some time and attention were given to special investigations concerning foot-and-mouth disease of cattle in cooperation with the Pathological Division, but as this subject has been treated at length in a Bureau publication (Circular 147), it need only be referred to here.

The subjects of hog diseases, Texas fever, cattle ticks, cattle-tick dips, anthrax, blackleg, glanders, swamp fever, cattle mange, infectious abortion, the internal and external parasites of sheep, the marking and branding of sheep, etc.. have also received more or less attention at the Experiment Station.

OTHER WORK.

The breeding investigations conducted in cooperation with the Animal Husbandry Office have given some interesting results. This work is presented in the part of this report which relates to the Animal Husbandry Office.

As in former years, large numbers of small experiment animals and a large quantity of green forage were raised at the Station. Several needed buildings of small size were constructed, and the second and completing story was added to the new laboratory.

THE ANIMAL HUSBANDRY OFFICE.

Mr. George M. Rommel, Animal Husbandman of the Bureau, directs the work of this office, which relates to the breeding and feeding of live stock and poultry, the supervision of pedigree record associations, etc.

HORSE BREEDING.

COLORADO WORK.

The stallion to follow Carmon in the cooperative horse-breeding experiments with the Colorado Experiment Station at Fort Collins has not yet been purchased, although a number of horses have been inspected, which have not proved sufficiently desirable to be used. It is hoped that a suitable stallion will be found in time for the 1910

season.

The purchasing board, acting as a board of survey, in August, 1908, condemned 19 animals in the stud, three of which were mares purchased in 1905, which have proved to be unsatisfactory breeders. With the exception of one filly owned by the experiment station, which was injured just before the sale, the condemned animals were sold or turned over to the Colorado Agricultural College for work purposes. The filly mentioned will be sold in the near future. Annual inspections for similar purposes are arranged for.

The high mortality of foals throughout the State was felt at Fort Collins, and serious losses occurred for no apparent reason, unless it was adverse climatic conditions.

VERMONT WORK.

The work at the Morgan Horse Farm, near Middlebury, Vt., in cooperation with the Vermont Experiment Station, is progressing satisfactorily, and the farm has been much more fortunate in the foals of 1909 than was the case in the Colorado work. Ten foals were dropped, out of twelve mares bred. The new sheds are proving satisfactory, but the accommodations will soon be crowded, and additional stable room will be needed. It is possible that the present facilities will suffice during the coming winter, but provision should be made in the near future for a total of 25 brood mares in addition to stallions and young stock.

The most important improvement during the year has been the installation of a first-class water system. It is the well-known pneumatic system, with a 15,000-gallon underground tank. The pump is run by an electric motor, which is equipped with an automatic starting and stopping device. Very little attention is needed, and the pressure in the mains is practically constant. The system not only makes it possible to supply water to any part of the farm, but gives adequate fire protection as well.

IOWA WORK.

The Shire and Clydesdale mares used in the experiments in cooperation with the Iowa Experiment Station are proving to have excellent endurance, especially in hot weather. They are noticeably fast walkers. Only one mare foaled during the fiscal year.

The station has added to the stud the Shire mares Wrydelands Starlight (37804), Wrydelands May (43904), and Stow Silver Streak (52348). They have had excellent show records in both England and America. All these mares have been reduced in flesh and have been bred to the Clydesdale stallion Kuroki (13214).

CLASSIFICATION FOR AMERICAN CARRIAGE HORSES.

The classification for American carriage horses which was offered at twelve state fairs in 1908 at the Department's suggestion, resulted in very interesting and instructive exhibits. The animals shown were not all one could wish in every case, but they were all one could expect. That the fair managers believe that the classification is a useful one is shown by the fact that, with very few exceptions, the classification is being offered by the same fairs for 1909, although no assistance is rendered by the Department except furnishing judges when requested. Besides the fairs which offered the classification last year, the Missouri State Fair offers the complete classification for 1909, whereas only a partial one was offered in 1908, and the classification is offered by three additional fairs, including the livestock show of the Alaska-Yukon-Pacific Exposition. Fourteen fairs of state or national importance have provided the classification for 1909. No change has been made in requirements and the classification stands as published in the revised edition of Bureau of Animal Industry Circular 113. Representatives of the Bureau attended each state fair offering the classification in 1908, and it is planned to continue this custom.

SHEEP BREEDING.

During the past year the range sheep-breeding work in cooperation with the Wyoming Experiment Station has been fairly satisfactory. During the lambing season in the spring some lambs were lost on account of the severe storms which continued for several days at a time, but the number lost was much less than it would have been if the new lambing sheds had not been available. The use of these sheds has proved to be a very good investment.

The flock was sheared earlier than in 1908, and owing to the heavy rains during the spring the wool was much cleaner and the percentage of shrinkage in scouring will probably be considerably less. The number of sheep shorn was 307, of which 291 were ewes, 7 mature rams, and 9 yearling rams.

The total number of lambs dropped in 1909 and living on July 15 was 137; ewe lambs, 62; ram lambs, 73; sex not reported, 2. It is proposed to reserve three of the yearling rams for breeding purposes and to sell the remainder.

CATTLE BREEDING.

MILKING SHORTHORNS.

The experiment in breeding milking Shorthorn cattle, carried on in cooperation with the Minnesota Experiment Station and individual breeders, has been continued, and the circuit now includes five herds, each of which is visited by the circuit superintendent for two days