PATHOGENIC PROTOZOA 4*5 



the history of some Trypanosoma. At the present time, however, it ap- 

 pears much more likely that they are more nearly related to the 

 haemosporidia than to the flagellates, and Laveran and Mesnil's view 

 assigning them to the genus Piroplasma, the same genus as the parasite 

 of Texas fever, may be accepted. 



Diseases due to Spirochceta 



Closely allied to Trypanosoma is the genus Spirochmta, a similar 

 flagellate belonging to the order Monadida. In its general cork-screw 

 shape it resembles Spirillum, one of the bacteria, but differs from this 

 by reason of its plastic body and general mode of life. Many different 

 species have been described, and considerable difference of opinion exists 

 as to whether they should be classed as bacteria or as protozoa. One 

 well-known form — Spirochceta obermeieri — has long been recognized as 

 the cause of relapsing fever, and has been recently shown to be the 

 cause of human tick fever in Africa, which is carried from man to 

 man by the tick (Ornithodorus moubata). The organism of relapsing 

 fever, however, does not seem to have a typical flagellate structure; 

 there is unmistakable evidence of transverse rather than longitudinal 

 division ; its nucleus is distributed like that of a bacillus, and Novy has 

 shown that it reacts like some bacteria during plasmolysis. The need 

 of an intermediate host in the case of African tick fever seems to be 

 the one distinctive protozoan characteristic. 



While Spirochosta ooermeieri is perhaps a doubtful protozoon, there 

 is less doubt in the case of other species, some of which have un- 

 questioned flagellate characters, including typical nuclear structures, 

 longitudinal division and the like, while in a number of species an 

 undulating membrane analogous to that of a trypanosome can be made 

 out. Some of the better known species are : Spirochceta dentium of the 

 mouth ; S. refringens of ulcerating tumors ; S. gallinorum a blood para- 

 site of fowls, and S. anodontce, parasitic in the crystalline style of the 

 mussel Anodonta mutabilis. A similar parasite, described first as S. 

 balbiani, is found in the crystalline style of the oyster, but it has so 

 many trypanosome characteristics that it is now called Trypanosoma 

 balbiani. It serves to illustrate the close relationship between these 

 two genera. 



It is to this group of parasites that Spirochceta (Treponema) 

 pallida, the cause of syphilis, belongs. The organism was discovered a 

 year ago, and since that time has been submitted to the widest range 

 of pathological research. A full life history has been published by 

 Siedlecki and Krzyszakowicz, and some of the stages described by them 

 are strikingly similar to those of Trypanosoma. Schaudinn regards it 

 as sufficiently distinct from other Spirochceta species to justify a new 

 generic name and calls it Treponema pallidum. 



