SOFT SORE 



259 



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 simi- 

 lar to those observed 

 when the organism is 

 in the tissues (Fig. 76), 

 but occasionally long 

 undivided filaments are 

 observed which Davis 

 regards as degenerative 

 forms. Within a com- 

 paratively short period 

 cultures undergo marked 

 degenerative changes, 

 and great irregularities 

 of form arid shape are to 

 be found. It would ap- 

 pear 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 demon- 

 strated. 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 con- 

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

 fact which is in conformity with the known facts as to the 

 transmission of the disease. 



1 We are indebted to Dr. Davis for the use of Figs. 75 and 76, 



j&.-'-v 



^x$ 



FIG. 76. Ducrey's bacillus from a 24-hour 

 culture in blood-bouillon, x 1500. 1 



