FIG. 11.-A tuberculous bull, known to pass tubercle bacilli with his feces. When tubercle bacilli can be detected in the feces they are probably numerous, because the opaque character of the material and the fact that the bacilli are isolated from each other and evenly distributed throughout the entire mass make it difficult to find them.

FIG. 12.

An exceptionally dangerous tuberculous cow. At the time her picture was taken she was daily passing a large number of tubercle bacilli with her feces. Her general condition is good and she shows no symptoms of tuberculosis. Without the tuberculin test she would not have been known to be tuberculous, and without other tests her uncommonly dangerous character would not have been suspected.

As no description can define the appearance of an animal as well as a photograph, the accompanying illustrations (figs. 10 to 19, inclusive), made from photographs, are presented to show the frequently excellent and seemingly healthy condition of dangerously tuberculous cattle. It must be added that the cattle represented in the pictures do not cough; they have excellent appetites and no visible or audible respiratory difficulties; in all respects they act like healthy animals, and perfect harmony exists between their healthy appearance and their healthy conduct. It is only when the tuberculin test is applied to them that their tuberculous condition is revealed, and it is only when the substances that are eliminated from their bodies feces, saliva, milk, etc. are subjected to microscopic and

FIG. 13.-A dangerous tuberculous cow. It is known that this cow began to expel tubercle bacilli with her feces as long as eighteen months before her picture was taken. condition is that of a fat beef animal.

Her

other tests that the proof is obtained of their dangerous character for public health and for the health of other animals.

It is not always possible to determine precisely how tubercle bacilli are expelled by individual tuberculous cattle; the tests for this purpose require too much time and careful observation for general practical application. It is well to assume that every tuberculous cow expels tubercle bacilli, because if she does not do so at one time she will do so sooner or later in the course of the disease.

The enormous tuberculous masses sometimes found on post-mortem examination in the bodies of cows like the subjects of these pictures cause great surprise, and demonstrate that life and seeming health

can be maintained under extremely adverse conditions that are of slow and gradual development, as tuberculosis or consumption.

Directly after the cow shown in figure 16 was removed from a dairy herd because she reacted with tuberculin and not because she showed symptoms of tuberculosis, a small nodule about the size of a pea was discovered under the skin of her udder. Examination of the milk from the quarter of the udder in which the nodule was located revealed the presence of numerous virulent tubercle bacilli. The cow was permitted to live some time, because it was desirable to use her infected milk for special investigations. When she was killed her udder was found to be in the condition shown in figure 17.

FIG. 16.-An exceptionally dangerous tuberculous cow. This cow, in addition to secreting highly virulent tuberculous milk, also expelled tubercle bacilli from her mouth and per rectum.

Cattle like those shown in the illustrations supply the best proof we can obtain of the possibly dangerous character of dairy cows that are not proved by a careful application of the tuberculin test to be free from tuberculosis. These cattle are in excellent condition; most of them are in better bodily condition than can be expected of ideal dairy cows that give large quantities of milk; they show no symptoms of disease, and act precisely like normal healthy animals. A cow like the subject of figure 16 shows that tuberculous cows with tuberculous udders may remain undetected until the tuberculin test is applied to them, and a cow like the subject of figure 18 proves conclusively that apparently healthy tuberculous cows may, at any time without previous warning, suffer an acute extension of the disease to

their udders, through which their milk becomes so badly infected with tubercle bacilli that its use in a raw state would be suicidal.

FIG. 17.-Sections of the tuberculous udder and a pubic lymph gland of the cow shown in figure 16. The pubic lymph glands are located directly behind and above the udder and usually show tuberculous lesions when the udder is affected.

We may conclude that the general appearance of tuberculous cattle, until the disease is near its last stages, or has become generalized,