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good; she has no cough that would attract the attention of the casual observer. Even if she were not affected with tuberculosis, her present condition, as shown by the picture, would have to be regarded as very good for an animal of her age.1

Cow No. 509 was tested with tuberculin in a dairy herd and found to be tuberculous about nine months ago. Directly after her removal from the herd, which was supplying milk to Washington, D. C., microscopic examinations showed the presence of tubercle bacilli in both her milk and fæces. In one quarter of her udder a small nodule about the size of

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FIG. 2.-Cow No. 509, in good condition and showing no symptoms of disease, recently in a herd supplying milk to Washington; tubercle bacilli present in both milk and fæces. (Schroeder, Circular 118, Bureau of Animal Industry, United States Department of Agriculture.)

a pea was found, the tuberculous character of which was not suspected until after she reached the Bureau Experiment Station. Guinea pigs inoculated with her milk and with butter made from her milk died affected with typical generalized tuberculosis. The butter made from her milk was ordinary salted butter, and in this the infection persisted

1 Since the above was written, cow No. 1 died very suddenly. When she was stabled for the night she appeared to be in her usual condition, and ate the whole of her evening feed; the next morning she was found dead. The post-mortem examination showed lesions of generalized advanced tuberculosis.

with undiminished virulence for forty-nine days. Tests are being made to determine how much longer than the time named tubercle bacilli will retain their virulence in ordinary salted butter.

The cow is seemingly in better physical condition than most dairy cows. Her appetite is good, she has no cough, and shows no symptoms of disease or distress.

She calved about six months before the picture was taken. Her calf remained with her until it was weaned; it was killed at the age of five months, and found on post-mortem examination to be affected with gen

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FIG. 3.-Cow No. 512, in good condition and showing no symptoms of disease; recently in a herd supplying milk to Washington; was scattering tubercle bacilli in a dangerous way. (Schroeder, Circular 118, Bureau of Animal Industry, United States Department of Agriculture.)

eralized tuberculosis. Four other calves, born of healthy cows, were also fed the milk of cow No. 509. One calf was fed one day, one three days, one seven days and one thirty days. The calves fed respectively one, three and seven days sucked the milk directly from the cow's udder, but were not allowed to be near her or to come in contact with tuberculous infection except at the time of feeding. The calf that was fed thirty days received the milk in a pail, and was never near tuberculous infection other than that contained in the milk. All four calves contracted tuberculosis.

Cow No. 512 was tested with tuberculin in a dairy herd and found to

be tuberculous eight months ago. Directly after her removal from the herd, which was supplying milk to Washington, D. C., microscopic examination showed that she was passing tubercle bacilli with her fæces. Her general condition is good, she has an excellent appetite, does not cough and does not show a single symptom of tuberculosis or other disease. Without a tuberculin test her tuberculous condition would not be suspected, and without the microscopic test of her fæces it would not be known that she is scattering tubercle bacilli in a dangerous way. She calved about three and one-half months before the picture was taken.

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FIG. 4.- Cow No. 518, recently found affected with tuberculosis in a herd supplying milk to Washington; apparently healthy, but actually scattering tubercle bacilli. (Schroeder, Cir. cular 118, Bureau of Animal Industry, United States Department of Agriculture.)

The record of cow No. 518 is identical with that of No. 512, with the exception that the tuberculin test which first demonstrated her tuberculous character was made one month later, and it is not known when she produced her last calf.

The record of cow No. 537 is identical with that of No. 512, excepting that the tuberculin test which first demonstrated her tuberculous character was made four months later, and it is not known when she produced her last calf.

Cow No. 552 was tested with tuberculin in a dairy herd about four months ago and found to be affected with tuberculosis. Directly after

her removal from the herd, which was supplying milk to Washington, D. C., microscopic examinations showed that she was passing tubercle bacilli with her fæces. Subcutaneous inoculation of guinea pigs with her fæces caused them to become affected with typical generalized tuberculosis. It is not known when she produced her last calf.

The significance of the inoculation of guinea pigs with her fæces must be judged in connection with the fact that the amount of fæces inoculated into each guinea pig is only a fraction of a grain. A cow of average size passes about 30 pounds of fæces each day, and the small amount

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FIG. 5.- Cow No. 537, recently condemned as tuberculous in a herd supplying milk to Washington; though apparently in good health, she was passing tubercle bacilli. (Schroeder, Circular 118, Bureau of Animal Industry, United States Department of Agriculture.)

inoculated into a guinea pig to test for the presence of tubercle bacilli contains many other bacteria, some of which, when injected under the skin, cause inflammatory processes that prevent the actual entrance of tubercle bacilli into the tissues in a way to cause their absorption and the production of tuberculosis.

The cows shown in the illustrations, relative to breed and visible condition, are fairly representative of those usually seen in the better class of dairy herds from which the milk supply of cities is derived. Few better and many much worse looking cows are found in urban and suburban herds. The simple fact that a cow is thin does not condemn

her. Dairy cows are not fat animals. Before her milk flow begins, a cow is subjected to the drain that accompanies the production and delivery of a calf; and afterwards the feed she eats is converted into milk, rather than deposited in her body as fat. Cows that lay on much fat while they are milking are rarely economical for dairy purposes.

In addition to cow No. 1, another old cow remained under observation at the experiment station a long time. She died last spring, after she had reached the age of twenty-one years.

Before her death it was

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FIG. 6.- Cow No. 552, found in a herd whose milk was sold in Washington; apparently healthy, but in fact dangerously tuberculous. (Schroeder, Circular 118, Bureau of Animal Industry, United States Department of Agriculture.)

established that she was scattering tubercle bacilli both through the mouth and through the rectum; and pure cultures of these germs, isolated from the tuberculosis lesions of guinea pigs inoculated with saliva and fæces, are now growing in the Pathological Division of the Bureau of Animal Industry. The tuberculous condition of the old cow was known six years before she died, but, notwithstanding her great age, she retained the semblance of health up to the last year of her life, during which she failed rapidly, became very thin, and suffered with a severe cough.

To the six pictures previously given one more of a dangerously tuberculous cow is added. This last picture is presented to show that a dangerously tuberculous cow may actually be in prime, fat, beef condition.

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