ACTIXOMYCES GROUP 373 



of many investigators, although a committee of the Pathological 

 Society has decided that it be retained. 



Organisms belonging to Leptothrix and Cladothrix are not 

 known to produce disease in animals. It seems to the writer that, 

 at the present time, an attempt to draw a distinction between 

 Nocardia and Actinomyces is impracticable. The genera are so 

 imperfectly known, and their life-history in many cases so imper- 

 fectly worked out, that it is difficult to know into which of the 

 two genera to place a particular organism. The genus name 

 Actinomyces will be here used to include both. 



Fig. 160. Streptothrix (Actinomyces) ccelicolor, a non-pathogenic tricho- 

 mycete from the soil. A ring colony on a semisolid medium showing filaments 

 and aerial hyphae (Miiller). 



Several organisms are included in this genus, as here dis- 

 cussed, that may be shown to belong to the bacilli and not to the 

 trichomycetes. 



Many species of organisms of this group are known from the 

 descriptions of a single author only. It is difficult to determine 

 from these descriptions how many are valid species and how many 

 merely synonyms. The facts seem to be that Actinomyces are 

 widely distributed in nature. They may be isolated in abundance 



