CLASSIFICATION OF ANAEROBIC BACTERIA 533 



the judgment, or shall we say to the taste, of those who have 

 themselves worked with the groups that they discuss. I am 

 totally unable to see how morphological criteria can possibly 

 be used to any logical end in the classification of the rods of 

 higher metabolism, or even of the main groups of anaerobes. 

 In 1902 Achalme found morphology of absolutely no use for the 

 differentiation of anaerobes. In 1905 von Hibler energetically 

 decried the use of morphology in anaerobic classification. In 

 analysis of the anaerobic group morphology has its place, and 

 can logically be used to distinguish types that are otherwise 

 similar. It can not, in my opinion, be used to unite groups 

 that are otherwise dissimilar. In the anaerobic group morpho- 

 logical criteria alone would hopelessly bewilder the student and 

 lead him to the correlation of fundamentally different types and 

 to the separation of sister rods of the same strain. Morphology 

 need, however, never be entirely discarded from classification. 

 The morphology of the anaerobes is, for a given species, so 

 characteristic, that if it be observed conscientiously, and if the 

 worker does not generalize too freely in formulating his descrip- 

 tion, it may well be used as a valuable descriptive character for 

 species, and as an auxiliary character for the description of 

 genera. It is in organizing the major groups of anaerobes that 

 morphology fails us. Professor Harvey M. Hall of the Botany 

 Department of this university suggests that after a logical and 

 fundamentally historical chemical classification has been made, 

 morphological characteristics will be found which will be con- 

 sistent with it. One must distinguish between different types 

 of morphological criteria. Gross form of rod and position of 

 spore are not fundamental morphological characters: they vary 

 greatly within the species. But a highly refined cytological 

 technique such as has never been generally applied to our organ- 

 isms might reveal consistent morphological characters. 



THE ANAEROBIC RODS 



In my opinion the most logical division of the bacterial rods — 

 the rods which split higher compounds and are not acid-fast — 

 is the physiological one of susceptibihty to free oxygen. Abihty 



