Chapter 1 



TERMINOLOGY, PHYLOGENY, AND TAXONOMY 



Because of their systematic position and their relationships to the 

 bacteria, on the one hand, and to the fungi, on the other, much confu- 

 sion has arisen concerning the taxonomic position of the actinomvcetes 

 This has been further compHcated by the varied terminology used in 

 different countries, and frequently even in the same country, to desig- 

 nate the genera and the species of this group of organisms. 



The confusion is due to a number of factors, the most important of 

 which may be summarized briefly as follows: 



1. In 1875, Ferdinand Cohn (72) designated a culture of a filamen- 

 tous organism found by R. Foerster in the concretions of the lacrymal 

 duct as Streptothrix Foersteri. Cohn emphasized the similarity of this 

 organism to the false-branching Leptothrix, on the one hand, and to the 

 true-branching fungi on the other. The photograph of the organism 

 as prepared by Cohn (Fig. 1) leaves no doubt that this was a true ac-. 

 tinomyces. Soon afterward, in 1877, an infectious agent in cattle dis- 

 covered by Bollinger (42) was named by Harz (166) Actinomyces 

 hovis, because the masses of filaments were arranged radially, which sug- 

 gested the name "actinomyces" or "ray fungus." Neither of these two 

 generic designations has been universally accepted, largely because the 

 first name (^Streptothrix') had been preempted, and the second QActino- 

 myces) has been meeting with much criticism, because the description 

 of the organism was based on its etiology rather than its morpholog)^ and 

 cultural characteristics, and furthermore no pure culture was obtained. 



2. Following these two basic contributions to our knowledge of the 

 actinomycetes, numerous investigators, comprising medical workers, 

 plant pathologists, botanists, and bacteriologists, devoted themselves to 

 the study of this group of organisms. This resulted in various overlap- 

 ping descriptions which frequently proved highly confusing, since dif- 

 ferent workers were interested in different aspects of the morphology, 

 physiology, or etiology of the organisms concerned. 



3. A large number of generic names were soon added to the first 

 two, without sufficient x:onsideration being given to the fundamental 

 aspects of the morphology and physiology of the organisms themselves. 

 The increasing number of generic designations were then further com- 

 plicated by a large number of species descriptions. These were based 

 either upon the natural substrate from which the organisms were isolated 

 or upon a single physiological property, such as odor or pigment pro- 

 duction when grown in a complex organic medium. 



