BACTERIA AND DISEASE 277 



Morphological differences are found under different cir- 

 cumstances, and within limits variation occurs according to 

 the environment. 



Cultivation on Various Media. Koch inoculated solid blood 

 serum with tubercular matter from an infected lymphatic 

 gland of a guinea-pig, and noticed the first signs of growth 

 in ten or twelve days in the form of whitish, scaly patches. 

 These enlarged and coalesced with neighbouring patches, 

 forming white, roughened, irregular masses. Nocard and 

 Roux showed that by adding f per cent, of glycerine to the 

 media commonly used in the laboratory, such as nutrient 

 agar or broth, the best growth is obtained. 



On glycerine broth or glycerine agar abundant growth ap- 

 pears at the end of seven or eight days. By continuous 

 sub-culture on glycerine agar the virulence of the bacillus is 

 diminished. But in fifteen days after inoculation of the 

 medium the culture equals in extent a culture of several 

 weeks' age on blood serum. 



Sub-cultures from glycerined media will grow in ordinary 

 broth without glycerine (Nocard, Roux, Crookshank). 



In alkaline broth to which a piece of boiled white of egg 

 was added Klein obtained copious growths, and found that 

 continued sub-culturing upon this medium also lessens the 

 virulence. 



Description of Cultivations: On glycerine agar minute 

 white colonies appear in about six days, raised and isolated, 

 and coalescing as time advances, forming a white lichenous 

 growth, fully developed in about two months. 



On glycerine broth a copious film appears on the surface 

 of the liquid, which if disturbed falls to the bottom of the 

 flask as a deposit. 



Spore Formation. In very old cultivations spore-like 

 bodies can be observed both in stained and unstained pre- 

 parations, but neither the irregular granules within the cap- 

 sule nor the unstained spaces between the granules are 



