1 6 SPIROCILETES. 



of syphilis gives rise in the body of the human host to 

 the formation of an antibody (copula or amboceptor) as 

 do the pathogenic bacteria. This form of immune sub- 

 stance has not been found in infections caused by 

 protozoa. 



It is to be hoped that further study of the life-history 

 and development of spirochsetes will throw definite 

 light on their true biological position. If the observa- 

 tjon of Leishman on the development of Sp. duttoni 

 into coccoid forms be confirmed, and if a similar change 

 can be shown to take place in other spirochaetes, as is 

 suggested by my own experience, their close relationship 

 to the bacteria will be manifest. 1 



In attempting to assign the spirochastes either to 

 the protozoa or the bacteria, it must be borne in 

 mind that there are several other kinds of organisms 

 known, about which there is equal uncertainty as to 

 their correct classification. Indeed, it has to be con- 

 fessed that there are no definite criteria, by which to 

 draw a line of division between the lowest forms of 

 animals and plants. This must be regarded as al- 

 most inevitable, since both animal and vegetable 

 kingdoms present to us as their lowest members uni- 

 cellular organisms of very simple structure, while it 

 is at least probable that at the beginning of things a 

 single form of living matter gave origin to both the 

 great divisions, animals and plants. 



MORPHOLOGY OF SPIROCHAETES. 



The minute structure of the larger spirochaetes has 

 been carefully observed in the species Sp. balbianii and 



1 The suggestion that spirochaetes are stages in the development 

 of a bacterial organism is referred to on page 42. Schaudinn's 

 original view that they constitute a stage in the life-history of a 

 trypanosome is now generally supposed to have been based on a 

 mistaken identification. (See Novy and MacNeal, Journ. Infect. 

 Dis., 1905,11,256; Sergent, Edm. and M., Ann. d. VInst. Pasteur, 

 1907.) 



