VACCINE-THERAPY 179 



The solution is made thus : 



Corallin ... ... ... ... 1 gramme. 



Methylene blue (saturated alcoholic 



solution) ... ... ... ... 120 c.c. 



Glycerin ... ... ... ... 20 c.c. 



Tuberculin. 



In 1890 Koch introduced his presumed cure for human 

 consumption — namely, tuberculin, which is prepared as 

 follows : A flat-bottomed flask containing 4 per cent, 

 glycerin-broth is inoculated with active B. tuberculosis 

 over the surface, and incubated at 37° C. for four weeks. 

 At the end of this period a heavy wrinkled growth 

 appears, and in two months the growth is ready for the 

 preparation of the tuberculin. 



The contents of several flasks prepared as above are 

 placed in a porcelain evaporating dish on a water-bath, and 

 concentrated to about a tenth of its original bulk, when 

 the glycerin content becomes about 40 per cent. 



Several varieties of tuberculin are prepared by other 

 workers, based upon Koch's original principle, and which 

 are used in bovine practice, not as a curative, but as a 

 diagnostic agent. 



Tuberculin as used for a Test for Tuberculosis. 



Tuberculin has proved of great value in assisting the 

 clinician to diagnose tuberculosis in the lower animals. 



The following are the principal methods in use : 



The subcutaneous test. 



The ophthalmic test. 



The cutaneous test. 



The Subcutaneous Test. — The subcutaneous injection of 

 tuberculin is by far the most satisfactory means of diagnosis 

 in veterinary practice. 



The cervical or scapular region is the usual site for 

 injection. The hair should be clipped over the part, and 



