148 ANNUAL REPORT OF THE Off. Doc. 



Should the lungs become involved the breathing may become 

 quickened and labored, with a dry troublesome cough. The lungs 

 are seldom the first seat of attack but become affected after the dis- 

 ease has made considerable progress in the abdominal organs. The 

 lymphatic glands, especially of the lower jaw and throat are fre- 

 quently found affected, with no lesions in other organs. In one of 

 our large abattoirs, out of a day's killing of about 6,000 hogs, 652 

 head were found to be infected only in the glands of the head and 

 intestines, 26 head showed extensive lesions in other organs causing 

 destruction of the carcasses. 



The importance of this disease must be considered from three 

 points of view, first, loss to the owner; second, effect upon the 

 available food supply ; third, the danger of communication to human 

 beings. 



The owner may sustain a gradual loss extending over a consider- 

 able period of time, by reason of the diminished milk production 

 from certain of his cows in which the disease may be gradually ad- 

 vancing. The loss becomes evident when an animal dies of the dis- 

 ease or when an apparently healthy animal is slaughtered and found 

 to be so badly affected as to be unfit for food. 



When we consider the value of the many thousands of animals that 

 die from this disease and the carcasses and parts of carcasses which 

 are annually condemned, its effect upon the food supply must be 

 apparent, as all such losses must ultimately fall upon the consumer. 



The danger of communication to human beings is largely through 

 milk from tuberculous cows. The many investigations which have 

 been conducted in connection with infantile tuberculosis, leave no 

 room for doubt that infected milk has been the cause in a large num- 

 ber of cases. It is also thought that a number of cases of the dis- 

 ease in adult persons could be reasonably ascribed to infantile in- 

 fection, the disease having remained latent for a period of years. If 

 tuberculosis was an actively progressive disease exhibiting marked 

 symptoms, it would no doubt receive prompt attention and vigorous 

 measures would be applied for its control and eradication from 

 every herd. Its insidious nature is one of the features which render 

 it difficult to combat. It attacks its victim without any manifesta- 

 tion of its presence until serious damage has been done. 



The most effective means, thus far discovered, for controlling this 

 disease is the periodical application of the tuberculin test. This 

 test, while not infallible, is remarkably accurate and has been uni- 

 versally^ adopted for the detection of tuberculosis in cattle. It is 

 the most valuable diagnostic agent thus far discovered and its value 

 has been increasingly established with its extended use. Tuberculin 

 in the form used for the subcutaneous method of testing, is a con- 

 centrated liquid which contains the toxic products of the tubercle 

 bacilli, but not the bacilli themselves. The bacilli are planted in a 

 specially prepared culture medium and allowed to develop until 

 the medium becomes impregnated with the products developed by 

 the activities of the germs. This medium is then sterilized at a 

 temperature above the boiling point of water in order to kill the 

 germs, which are then filtered out. The resulting product, being 

 absolutely sterile, cannot produce the disease, nor will it cause any 

 derangement or show any ill effects when injected into a healthy 



