DISEASES CAUSED BY SPIROCILETES 593 



of these microorganisms have the power of multiplication by transverse 

 fission. They possess flagella and, in the case of some of them at least, 

 definite immune bodies can be demonstrated in the serum of infected 

 subjects similar to those produced by bacteria during infection. The 

 undulating membranes and the definite differentiation between nucleus 

 and cytoplasm claimed for them by some observers have not been uni- 

 formly confirmed, and their similarity to the trypanosomes has not 

 therefore been established. On the other hand, none of these micro- 

 organisms has so far been successfully cultivated upon artificial media, 

 with the exception of the spirilla which occur in Vincent's angina. For 

 some of the diseases caused by this class of parasites, moreover, trans- 

 mission by an intermediate host, in which the spirilla undergo multipli- 

 cation, has been definitely shown, a fact which corresponds with the 

 conditions observed in many protozoan infections. Upon a careful re- 

 view of these various data, it seems to be fully justified, on the basis 

 of our present knowledge, to group these microorganisms, as Kolle and 

 Hetsch ^ have done, in a class between bacteria and protozoa. 



The terms spirochsete and spirillum have been indiscriminately used. 

 In the original classification of Migula the difference between the two 

 groups was based upon the rigidity of the cell body in the case of the 

 spirilla and the sinuous or flexible nature of the cell in the case of the 

 spirochaetse. Although the term spirillum is still colloquially used for 

 some members of this group, merely because of past usage, it would be 

 better to speak of all the microorganisms here grouped together by the 

 term "spirochsetes." 



SYPHILIS AND SPIROCH^TA PALLIDA 



{Treponema pallidum) 



The peculiar manifestations of syphilis, its mode of transmission, 

 and the fact that its primary lesion was always located at the point 

 of contact with a preceding case, have always stamped it as unques- 

 tionably infectious in nature. Until very recently the microorgan- 

 ism which gives ri^e to syphilis was unknown. Many bacteriologists 

 had attacked the problem and many microorganisms for which defi- 

 nite etiological importance was claimed had been described. Most of 

 these announcements, however, aroused little more than a sensational 

 interest and received no satisfactory confirmation. A bacillus described 



^ Kolle und Hetsch, "Die experimentelle Bakt.," Berlin, 1906. 



