i 5 6 SCIENCE PROGRESS 



unsatisfactory nature of both the reagents and tests at present 

 applicable. In the end, a chitinoid substance appeared to be 

 present in the periplast and not fungus-cellulose. This is in 

 favour of the protozoal or animal nature of Spirochetes. 



This periplast is, however, quite flexible, more so than in 

 the genus Spirillum. This question of rigidity occasionally has 

 been used as a test of the protozoal or bacterial nature of a 

 protist organism. Again, the consideration of cultures or pre- 

 parations of artificial media in which Spirochaetes might be 

 reared is more or less concerned with the bacterial or other 

 nature of these organisms. So far as I know, no successful 

 medium capable of sustaining the life of any Spirochete for 

 any length of time has yet been found. This has been re- 

 marked by Novy, Perrin, the present writer, and others. Those 

 Spirochaetes on which the experiments have been tried are 

 said to be implasmolysable. 



It has been stated (3) that S. duttoni is a Protozoon, because 

 regular, recurrent relapses of tick fever result from its presence 

 in the system. 



These points of difference, however, must only be treated 

 broadly and not emphasised too much singly, for doubtless 

 exceptions to some of them can be found. 



We may now briefly summarise these and other relevant 

 characteristics under two heads, taking first the principal 

 characteristics that rather suggest the inclusion of the Spiro- 

 chaetes among the Bacteria : 



(«) The diffuse condition of the nucleus, directly comparable 

 with that of Spirilla and somewhat like that of Bacillus butschlii 

 (Schaudinn). 



(b) The occurrence of transverse fission among Spirochaetes. 



(c) The absence of a blepharoplast in the form in which it is 

 found in Trypanosomata. 



As characteristics favouring the inclusion of Spirochaetes in 

 the Protozoa, we may note : 



(a) The possession of a membrane. 



(b) The occurrence of longitudinal fission. 



(c) They are implasmolysable. 



(d) The inability, up to the present, to find suitable artificial 

 media in which Spirochaetes may be kept alive. 



(e) The presence of a small amount of chitinoid substance in 

 the periplast and membrane. 



