PHILIP HADLEY loi 



The acknowledgment of the existence of definite cyclostages in the development 

 of the bacterial culture naturally concerns our appraisal of the thing that has passed 

 as the "normal" bacterial type. The observations already presented dealing with this 

 subject can lead us only to the view that the older notions of normality and immu- 

 tability of culture type have determined a highly repressive and dangerous influence 

 on the development of bacteriology — an influence which, even at the time of writing, 

 is still menacing the progress of the science. The present conceptions of "normal type," 

 "normal colony," and "normal" cytology we owe to the influence of monomorphism 

 which, even in most recent textbooks, still clings like a barnacle to modern bacteri- 

 ology. According to its dictates, whatever departs from the "normal" must be re- 

 garded as an "involution form," a degeneration form, a mutant, or a contamination. 

 On the other hand, whatever form of culture the bacteriologist succeeds in causing to 

 develop most freely in his carefully standardized media, and under other standard- 

 ized conditions of growth which he imposes, are "normal" cultures, while aberrant 

 forms are of little consequence. In order that there may be no lack of means for mak- 

 ing the species recognizable, we assiduously fill out data on neatly designed descriptive 

 charts — all dealing with the "normal" type, usually the S. Are we, then, forced to the 

 conclusion that cultures of the and R forms are not normal cultures? 



It is indeed time that we revised our notions on "normality" in bacterial species. 

 The results of many studies dealing intentionafly or unintentionally with microbic 

 dissociation force the conclusion that there is no such thing as "normal" type in the 

 usual meaning of the term. The O type cultures are no less normal than the S; nor 

 the R type cultures less normal than the O. They are all normal, and can be regarded 

 in no other light than that of isolated states or stages of the bacterial species in its 

 progress through the cyclode. And it may be said in passing that this view may no 

 doubt be held equally for the filtrable forms of bacteria. These have often been re- 

 ferred to as "fragments," or as minute "fractions," of the "normal" cell, and endowed 

 with the power of "regeneration" into the original form. We shall perhaps do well to 

 question whether these minute living elements may not represent one or more definite 

 units (cyclostages) in the reproductive history of the species. From this viewpoint, 

 whether we deal with filtrable or non-filtrable forms, it is essential that we should 

 cease to regard "normality" in the old, absolute sense, but should come to regard the 

 characters of bacteria as related to definite stages in their development. Thus we may 

 have a normal growth of B. typhosus on plain agar, or on phenol agar, or at 42° C, or 

 in immune serum, or under reduced oxygen tension. The growth is normal with ref- 

 erence to a certain condition or environment, although it is likely to differ in each of 

 the conditions mentioned above. That "pathological" growth forms may occur can- 

 not be doubted; but at present we are not in a position to recognize them — any more 

 than we are in a position to recognize bacterial mutations, so called — until we have 

 gained a fundamental knowledge of the nature, limits, and sec^uence of cyclogenic 

 variation. 



