86 BACTERIOI/OGICAL, EXAMINATION OF MIL,K. 



only upon solid culture media of cattle blood serum and 

 glycerine agar. They grow remarkably slow, and, in 

 spite of great dilution of the milk, a sample from which 

 the inoculation is made, the media become very quickly 

 overgrown by the rapid and luxurious growing 

 saprophytic bacteria of the milk. For the de- 

 termination of the tubercle bacilli the solid cul- 

 ture media are not so well adapted as the fluid 

 ones ; of the latter, especially the Nocard bouil- 

 lon (nutrient bouillon with 6 per cent glycerine and 

 3 per cent gelatine). A large number of samples^ are 

 suitably started and kept for at least three Weeks at 37 

 degrees in an incubator. From the colonies developed 

 in one manner or another, microscopic preparations are 

 made and stained in the usual manner. 



More accurate information is gained by experimenting 

 on living animals to determine the presence of tubercle 

 bacilli in the milk, or whether their number is ■ sufficient 

 when the milk is consumed to produce tuberculosis. 

 Guinea pigs and also rabbits, are fed with the suspected 

 milk and after 8-10 weeks examined for tuberculosis of 

 the intestines, mesenteric glands and the liver. Instead 

 of feeding, intraperitoneal injections can be made. The 

 iediment secured from centrifugalizing impure milk is 

 especially adapted for this purpose. The presence of 

 tuberculosis is diagnosticated by sections of the dead or 

 slaughtered animals. 



2. THE CHOLERA BACILLUS. 



The demonstration of it presents great difficulty and 

 must be done according to the proper methods of exam- 

 ining water. Neither staining, appearance, nor animal ex- 

 perimentation are especially characteristic. Its identity 

 can be confirmed only through cultivation. 



For the diagnosis of the cholera bacillus a method 



