Pathogenesis and Specificity 425 



be undoubtedly contagious. The greatest number of the 

 organisms are found in the tissues especially the liver of 

 still-born infants with congenital syphilis. 



Cultivation. No method has been invented by which 

 artificial cultivation of the spirochaetes can be accomplished. 

 This is unfortunate, as it limits our field of experimentation. 



The nearest approach to successful cultivation was ac- 

 complished by Levaditi and Mclntosh,* who, deriving 

 the organism from an experimental primary lesion in a 

 monkey (Macacus rhesus) , carried it through several genera- 

 tions in collodion sacs inclosed in the peritoneal cavity of 

 other monkeys (Macacus cynomolgus) and in the peritoneal 

 cavity of rabbits. They were unable, however, to secure 

 the spirochaete in pure culture, having it continually mixed 

 with other organisms from the primary lesion. In the 

 mixture, however, they were able to cultivate it for genera- 

 tions and study its morphology and behavior. During 

 cultivation its virulence was lost. 



Pathogenesis and Specificity. There can no longer be 

 any doubt about the causal relation of Treponema pallidum 

 to syphilis. It is unknown in every other relation ; it has ap- 

 peared in every required relation, and thus has as completely 

 identified itself with the disease as is possible with organisms 

 that cannot be cultivated. It bears the same relation to 

 syphilis that Bacillus leprae does to leprosy, or Spirochaete 

 obermeieri does to relapsing fever. Treponema pallidum is 

 not only pathogenic for man, but, as has been already 

 shown, can also be successfully implanted into skins of 

 chimpanzees, macaques, and rabbits, and into the cornea 

 of rabbits, guinea-pigs, and other experiment "animals. As 

 syphilis is, however, unknown to occur under natural con- 

 ditions, except in man, it may be looked upon as a human 

 disease. 



The organism enters the body through a local breach of 

 continuity of the superficial tissues, except in experimental 

 and congenital infections, where it may immediately reach 

 the blood. 



In ordinary acquired syphilis the point of entrance shows 

 the first manifestations of the disease after a period of 

 primary incubation about three weeks long, in what is 

 known as the primary lesion or chancre. This appears as a 



* "Ann. de 1'Inst. Pasteur," 1907, p. 784. 



