1912.] On the Systematic Position of the Spirochcets. 187 



First, concerning the criteria which may be employed to decide the 

 systematic position of the Spirochaets. There is, in my opinion, but one 

 kind of evidence which can lead to a correct verdict. Judgment — if it is to 

 be conclusive — must be given upon morphological evidence. The classifica- 

 tion of all living beings is based ultimately upon morphology — using the 

 word in its widest sense to mean the study of the forms of organisms at all 

 stages in their life-histories. If the Spirochaets are to enter our artificial 

 system of classification, they must do so on the same terms as other 

 organisms. " Systematic position " must be judged by the same standard 

 throughout, otherwise the system would be inconsistent, and the term would 

 cease to have any definite meaning. It is, of course, possible to characterize 

 the Spirochaets by certain of their physiological, pathological, or chemical 

 attributes. But to attempt to enrol them in the system of organized beings 

 by virtue of such attributes alone would involve the reclassification of all 

 other living beings in the same terms. 



Secondly, I think the following postulate must also be granted. To 

 determine the systematic position of any group of organisms it is necessary 

 to have accurate knowledge of their structure and life-histories ; and we must 

 have this knowledge not only of the group in question, but also of all the 

 other groups which it may conceivably resemble. This means, in the present 

 case, that to determine the systematic position of the Spirochaets it is necessary 

 to possess accurate knowledge of the morphology of the Spirochaets, the 

 Flagellata, the Bacteria, and the Cyanophyceae. Without such knowledge it is 

 not possible to assign the Spirochaets a definite place in the present system of 

 classification. 



These two postulates are, to my mind, so indisputable that they are 

 almost platitudes. Nevertheless, it has become apparent to me, from the 

 work of others, that they are neither recognised nor accepted universally. I 

 have particularly emphasized them because my conclusions as to the 

 systematic position of the Spirochaets depend upon the recognition of their 

 validity. 



Desiring to determine the systematic position of the Spirochaets, I have, in 

 accordance with my convictions, endeavoured to study the morphology of all 

 the chief types of Spirochset. Four different genera of these may be dis- 

 tinguished* — Spirochceta Ehrenberg, Cristispira Gross, Treponema Schaudinn, 



* Gross is in complete agreement with me regarding the existence of these four 

 different types. But he regards Spironema as the correct name of the set of forms 

 which I call Treponema. In addition to these two names, more than half-a-dozen others 

 have been given to these organisms — collectively or severally. I may mention the 

 following : — Spirochceta, Spirillum, Vibrio, Trypanosoma, Microspironerna, Borrelia 

 Spiroschaudinnia. The nomenclature is still in great confusion. 



o 2 



