12 SPIROCILETES. 



dated. Indeed, owing to the minute size and feeble 

 staining properties of the latter organisms, it is difficult 

 to recognise more than their shape and movements. 

 Details of finer structure, which might throw light on 

 their true nature, are as yet wanting. The type of the 

 smaller spirochaetes may be seen in the organism associ- 

 ated with the disease called relapsing fever, usually 

 called Spirillum or Spiroch&ta obermeieri, after its dis- 

 coverer, but perhaps more correctly on the basis of 

 recent biological nomenclature, Spirochceta recurrentis, 

 the spirochaete of recurrent fever. This organism was 

 for many years regarded as a bacterium and placed in 

 the same class as the spirillum or vibrio of cholera. It 

 does not seem proved so far that this classification is 

 incorrect, and the question is still at issue, names of 

 weight being found on both sides in the controversy 

 as to the protozoan or bacterial nature of the smaller 

 spirochaetes. Even the larger spirochaetes have by some 

 been assigned to the bacteria as, for example, by 

 Schwellengrebel, who points out the close resemblance 

 between an organism, such as Sp. balbianii and some of 

 the larger spirilla, such as Spirillum giganteum (Spm. 

 volutans) . I hope to show in subsequent pages reasons 

 for thinking that this view is probably correct. 



With regard to the larger spirochaetes, it is certainly 

 natural to anyone who observes the extreme activity 

 of movement exhibited by such an organism as Sp. 

 anodontcz, to regard it as prima facie an animal. This 

 vigour of movement, however, does not by itself con- 

 stitute an argument of appreciable weight, for among 

 the spirilla, which are generally admitted to be bacterial, 

 very active movement may be observed. Nevertheless, 

 there is some difference between the two classes in this 

 respect; for while the spirochaetes perform vigorous 

 lashing movements in which the whole body is bent to- 



