LECTURE XXXVII. 

 THE TUBERCULIN TEST FOR TUBERCULOSIS. 



Tuberculin is usually seen in fluid form and is then a thin, 

 watery, slraw-colored fluid, slightly more viscid than water, due 

 to the presence of glycerine used in making up the solution. 



Tuberculin is a chemical product from the bodies of the 

 bacilli of tuberculosis, and is made as follows : a certain kind of 

 broth is infected with the bacilli of tuberculosis. The bacilli are 

 then allowed to multiply and grow in this medium until it has 

 become charged with this germ product, tuberculin. The whole 

 fluid is then passed through a porcelain filter and heated to kill 

 any germs that may possibly have passed through a defective 

 filter. It is therefore not only germ-free, but has also been raised 

 to a high temperature and cannot be infectious. 



Effect on cattle. — Careful experiments have demonstrated 

 that tuberculin has no important effect, favorable or otherwise, 

 upon the health or milk flow of sound cattle ; and that the effect 

 on tuberculous cattle is favorable rather than otherwise. An ex- 

 periment was conducted at the Minnesota Experiment Station a 

 few years ago, which included 23 sound and 5 tuberculous cows, 

 and compared the total milk flow and total butter fat of the herd 

 for the week prior to test with the week of test. In this experi- 

 ment the cattle were given ordinary handling, neither very rough 

 nor unusually gentle. 



There was a moderate decrease in the milk flow during the 

 two days of test, not more than could be easily accounted for by 

 unusual handling of the cattle and the presence of strangers. 

 This decrease was almost made up during the succeeding five days. 

 There was a slight increase of Initter fat during the week of test. 

 Both variations were easily within the limits of normal variation. 



The experiment with the five tuberculous cows gave about 

 the same results, the difference being easily within the limits of 

 normal variations, neither the total milk flow nor total butter fat 



