Pathogenesis 421 



no relation between the cells and the bacilli. As a rule, they are 

 free, sometimes they are inclosed in leukocytes. The bacilli are not 

 motile, have no flagella and do not form spores. 



Staining. — ^The organisms are somewhat difficult to stain, as they 

 do not retain the color well, giving it up quickly when washe^. 

 They do not stain by Gram's method. 



Cultivation. — The first successful isolation and cultivation of the 

 organism seems to have been by Benzanfon, Griffon and Le Sourd* 

 upon a culture-medium consisting of rabbits' blood i part, and agar- 

 agar 2 parts. Davis t has been equally successful in cultivating the 

 organism upon this medium. His method was as follows : 



"Tubes of 2 per cent, agar, reaction + 1.5, were melted and 

 mixed with fresh rabbits' blood drawn under aseptic precautions, 



'^mi0 



Fig. 143. — Smear of pus of chancroid of penis stained with carbol-fuchsin 

 and briefly decolorized by alcohol. X 1500 (Davis). (Photomicrograph by 

 Mr. L. S. Brown.) 



in the proportion of two-thirds agar to one-third blood, and slanted 

 while in a fluid state. At a later period tubes of rabbits' blood-serum 

 uncoagulated, also rabbits' blood bouillon, one-third blood to two- 

 thirds bouillon, were used, and gave equally satisfactory results. 

 By employing small tubes of freshly drawn human blood, pure cul- 

 tures were obtained in several instances from genital lesions, direct, 

 without any special cleansing of the ulcerated surface. This, I 

 believe, is the best medium for obtaining cultures from a source open 

 to contamination, the fresh blood apparently inhibiting to a certain 

 extent the growth of extraneous organisms." , 



No growth takes place upon ordinary culture-media under either 

 aerobic or anaerobic conditions. 



Cultiures are best obtained by puncturing an unopened bubo with 

 a sterile needle and planting the pus directly and immediately upon 

 the special medium which should have been warmed in the incubator 



* "Ann. de Dermat. et de Syphilog.," 1901, 11, p. i. 

 tLoc. cit. 



