THE NOMENCLATURE OF BACTERIA. 119 



done in text-books, has failed absolutely. We can un- 

 derstand and know the pathogenic varieties only if we 

 study simultaneously the non-pathogenic, from which the 

 former have once originated and still always originate 1 

 (see Pest). 



The doctrine of the absolute constancy of bacteria, 

 which for ten years was almost a dogma, is now scarcely 

 at all seriously advocated. 



II. The Nomenclature of Bacteria. 



The nomenclature at present employed in bacteriologic 

 works written by medical men is characterized by a limit- 

 less arbitrariness and inconsistency. Since these nomen- 

 clators often possess absolutely no sentiment for their 

 arbitrariness, and the simple rules of scientific nomen- 

 clature are often entirely unknown to them, I allow 

 myself to set down, as briefly as possible, the most essential 

 rules, which are, by international agreement, accepted by 

 all educated peoples, especially as they bear upon bacteri- 

 ology. 



1. Every plant and also every fission-fungus belongs to 

 a species, every species to a genus, every genus to a family. 



2. Following the precedent of Linne, every vegetable or 

 animal organism, therefore every variety of bacterium, 

 should have two Latin names : the first designating the 

 genus to which the concerned organism belongs, which 

 name is a substantive ; the second indicating the variety 

 (species), and being an adjective (not two) or the genitive of 

 a substantive, only rarely a substantive in the nominative 

 case. Thus, in the genus bacillus belong the species Bac. 

 subtilis (hay bacillus), also the species Bac. anthracis 

 (anthrax bacillus), and Bac. megatherium. 



3. Genera must only be founded upon important mor- 

 phologic characteristics; so-called " biologic genera, " such 

 as photobacterium for all light-emitting bacteria, pyo- 

 bacterium for rods causing suppuration, etc. , are only cal- 

 culated to produce confusion. 



1 If the pathologist may, perhaps, say that the pathogenic bacteria 

 alone interest him, such a statement as I have often heard from the 

 mouth" of a hygienist is almost beyond understanding. 



