CLASSIFICATION 351 



We are unwilling to decide on the systematic position of the actino- 

 mycetes but since most bacteriologists classify them in the order 

 Actinomycetales of Class Schizomycetes, we shall so consider them. 

 The term actinomycete we write in the lower case to indicate that it 

 is not used in a taxonomic sense but somewhat in the manner we 

 would use yeast or mold. It includes all the Actinomycetales except 

 the Mycobacteriaceae. See page 353. 



Petruschky proposed some years ago an arrangement which is still 

 followed at least in part by some textbooks in bacteriology. He 

 made a separate class of fungi characterized by the formation of very 

 fine filaments which he designated as Trichomycetes. This includes 

 four genera: Actinomyces, having forms with true branching and 

 forming "clubs" in infected tissues; Streptothrix, with true branching 

 but not forming "clubs"; Cladothrix, with false branching; and Lep- 

 tothrix, with no branching. But as will be pointed out later, the 

 formation of "clubs" in the tissues is not a reliable character and 

 certainly not sufficiently specific to be used for generic differentiation. 

 And Cladothrix and Leptothrix are ensheathed iron bacteria bearing 

 no similarity to the actinomycetes but rather closely related to the 

 blue-green algae. There is, therefore, no good reason for continuing 

 Petruschky's classification. 



. It is very difficult to read the literature on this group of microor- 

 ganisms intelligently because of the multiplicity of names which 

 have been applied, sometimes to the group as a whole, sometimes to 

 portions of it. The following generic names are used synonymously 

 with the actinomycetes : Streptothrix, Cladothrix, Oospora, Nocardia, 

 Discomyces, Actinomyces. 



The name Streptothrix was applied by Cohn to the first species of 

 the group to be discovered, Streptothrix Foersteri. This name was, 

 however, previously used to designate one of the higher molds and is, 

 therefore, not eligible. It has, however, been used by many early 

 medical authors to designate the entire genus and, as indicated above, 

 by numerous bacteriologists, following Petruschky, to designate those 

 pathogenic forms not producing "clubs" in tissues. 



The name Cladothrix was first applied to a group of the iron bac- 

 teria of which Cladothrix dichotonia is the type species. This is an 

 organism composed of chains of cells in a sheath, showing false 

 branching. No one acquainted with this organism would consider it 

 closely related to the actinomycetes. Nevertheless, Eppinger named 

 the acidfast actinomycete which he discovered C. asteroides, under 

 the mistaken impression that it exhibited false branching, and this 

 name has been handed down through the literature. 



