364 ACTINOMYCETES 



museums and these aerobic and saprophytic species are often de- 

 scribed in textbooks and in systematic treatises as the cause of 

 actinomycosis. However, in recent years the correct idea, that the 

 ordinary actinomycosis is caused by the bacteria-hke anaerobic 

 actinomycete, has been generally accepted. The medical aspects of 

 this genus are discussed elsewhere. See Chapter III for methods of 

 isolation and culturing this genus. The generic name Cohnistrepto- 

 thrix has been used by Brumpt and other writers to mean the same 

 as Actinomyces in this restricted sense and by 0rskov to include 

 conidia-forming aerobic actinomycetes. It is invalid in either sense. 

 Rosebury ^- has recently written an extensive review on A. bovis. 



Nocardia. This generic term, often incorrectly used to include all 

 the actinomycetes, has been retained by Waksman and Henrici ^" 

 to include those aerobic species which fragment into arthrospores 

 readily (but usually not so readily as Actinomyces) and also which 

 do not form true conidia. Like in Actinomyces the arthrospores con- 

 tinue to divide by fission and species of Nocardia resemble Myco- 

 bacterium or Corynebacterium very closely. Many species, both 

 pathogenic and non-pathogenic, are acidfast. They are more acid- 

 fast in tissue than in culture but they are partially so in culture 

 media, especially in milk, much like some of the saprophytic Myco- 

 bacteria. Species of Nocardia can be readily isolated from soil and 

 some of these are found to be pathogenic to animals. All the acid- 

 fast species seem to be able to utilize hydrocarbons and it is easy to 

 isolate saprophytic species with enrichment media whose only carbon 

 source is paraffin wax. Replicates of ten tubes of such media inocu- 

 lated with 1 ml. of 1/10,000 or 1/100,000 dilutions of several Minne- 

 sota soils showed growth of Nocardia in most tubes, hence they must 

 be very numerous in soils. Jensen ^^ has made a study of Nocardia 

 species in soils. The generic term Proactinomyces is sometimes used 

 in the same sense as Nocardia. Shchepkina ^^ has made the surprising 

 observation that Nocardia was found as an endoparasite in cotton 

 fibers. Not all species isolated from soil, however, are able to dissolve 

 cellulose, although many of them do so. Pathogenic species of No- 

 cardia are discussed in the following chapter. 



Micromonospora. This is, as far as is known, a purely saprophytic 

 genus. First named by 0rskov,^® in 1923, to include those aerobic 

 forms in which the conidia were borne singly, it remained practically 

 unknown until Jensen,^- ^° in 1930 and 1932, showed that many species 

 w^ere common in soil. More recently, "Waksman, Umbreit, and Cor- 

 don ^^ found that thermophilic Micromonosporae were common in 

 composts and seemed to be active in organic matter decomposition 



