CULTIVATION OF BACILLUS 265 



Sourd obtained pure cultures in four cases, the medium used 

 being a mixture of rabbit's blood and agar, in the proportion of 

 one part of the former to two of the latter. The blood is added 

 to the agar in the melted condition at 45° C, and the tubes 

 are then sloped. Davis confirms these results, and finds that 

 another good medium is freshly-drawn human blood distributed 

 in small tubes ; this method is specially suitable, as the blood 

 inhibits the growth of various extraneous organisms. On the 

 solid medium (blood-agar) the growth appears in the form of 

 small round globules, which attain their complete development 

 in forty- eight hours, having then a diameter of 1 to 2 mm. ; the 

 colonies do not become confluent. Microscopic examination of 

 these colonies, which are dissociated with some difficulty, shows 

 appearances similar to those observed when the organism is in 

 the tissues (Fig. 72), but occasionally long undivided filaments are 

 observed which Davis regards as degenerative forms. Within a 

 comparatively short period cultures undergo marked degenera- 

 tive changes, and great irregularities of form and shape are to be 

 found. It would appear that a comparatively large amount of 

 blood is necessary for the growth of this organism, and even 

 sub-cultures on the ordinary media, including blood-serum media, 

 give negative results. Inoculation of the ordinary laboratory 

 animals is not attended by any result, but it has been found 

 that some monkeys are susceptible, small ulcerations being 

 produced by superficial inoculation, and in these the organism 

 can be demonstrated. Tomasczewski cultivated the organism 

 for several generations, and reproduced the disease by inoculation 

 of the human subject. The causal relationship of this bacillus 

 must therefore be considered as completely established, and the 

 conditions under which it grows show it to be a strict parasite 

 under natural conditions — a fact which is in conformity with 

 the known facts as to the transmission of the disease. 



