GENERAL CHARACTERS OF SPIROCILETES. 15 



certainly striking, but is not in itself a strong argument 

 for combining them in a single group. The possession 

 of an undulating membrane by these minute organisms 

 is certainly doubtful, and the presence or absence of 

 flagella has little weight in this connection, except as an 

 arbitrary ground of classification. The question as to 

 the multiplication of these little organisms by lon- 

 gitudinal or transverse division is still undecided; but 

 the formation of a fine thread at the point of divi- 

 sion seems to be established, whereas bacteria divide by 

 means of a distinct septum. The argument from the 

 possibility of cultivation on artificial media has just 

 been noticed to be valueless, and indeed some of the 

 small spirochaetes have, if the claims of various writers 

 are to be believed, been successfully grown in the lab- 

 oratory. The conveyance of some of the pathogenic 

 spirochaetes by biting insects (ticks) has been used as 

 a proof of their animal nature, but can hardly be re- 

 garded as a conclusive argument ; for it has not been 

 proved that they undergo any constant process of 

 development within these hosts. 



A stronger argument has been drawn from the action 

 of certain chemical reagents on small spirochaetes. Thus 

 it is said that cobra-venom, taurocholate of sodium, 

 saponin, and pancreatic extract destroy spirochaetes 

 and protozoa, but do not affect bacteria. Spirochaetes 

 are little affected, however, by distilled water or by 

 concentrated salt-solution. It is also asserted that 

 whereas bacteriolysins are thermostable (not destroyed 

 by heat), the corresponding substances which act on 

 spirilla (spirochsetes) are thermolabile, thus resembling 

 the haemolysins. On the other hand, the action of 

 immune serum in producing agglomeration or aggluti- 

 nation of spirochaetes is like that exerted upon bacterial 

 organisms; and Sp. pallida if this be really the cause 



