Chapter I — 5 — Taxonomy 



siLNiKov (234, 236), and in many of the earlier (310) and more recent 

 papers (17-20, 106-108, 1 1 1-1 13, 185-192). It is sufiicient here to sum- 

 marize briefly some of the outstanding facts which led to our present 

 knowledge of the terminology and classification of the actinomvcetes. 

 More detailed information concerning the nature, occurrence, and im- 

 portance of certain special groups, notably those that produce animal and 

 plant diseases, the antagonistic forms, and the thermophilic types, will 

 be found in other sections of this monograph. 



A word must be said here concernina recognition of individual 

 species. At one time it was believed that only very few species of actino- 

 mycetes are found in nature. This belief was based upon observations 

 of the growth of these organisms on complex organic media or upon the 

 appearance presented by the organisms in the substrate from which they 

 were isolated. The presence of a white aerial mycelium was believed 

 to indicate an alhus type; production of a black or brown pigment led 

 to recognition of the chromogenus type; production of a characteristic 

 musty odor gave rise to the odorifer type; when a culture was isolated 

 from an actinomycotic lesion, it was called the hovis type, while an iso- 

 late from a scabby potato was considered as the scabies type. The intro- 

 duction of differential, especially synthetic, media brought out the great 

 variability of the actinomycetes. This frequently led to a multiplicity 

 of names and descriptions based upon minor cultural differences on 

 various media. Thus, we have names after all the colors of the rainbow, 

 such as "albus," "ruber," "roseus," "flavus," "glaucus," "viridis," "laven- 

 dulae," "violaceus," "cyaneus," "niger," and many synonyms of these. 



Fortunately, sufficient information has now accumulated on the mor- 

 phology of the actinomycetes to justify the separation of this large and 

 highly heterogeneous group of organisms into several genera; cultural, 

 physiological, and often ecological characteristics may be utilized for 

 their separation into species. 



Synonyms of Generic Names of Actinomycetes:— It is hardly neces- 

 sary to attempt a complete survey of all the generic and specific names 

 that have ever been given to the group of actinomycetes as a whole or to 

 certain constituent forms in particular. In some cases, these names have 

 also been used to designate certain true fungi or true bacteria; in other 

 cases, the names were simple synonyms. Some of the more common 

 designations of the group and their historical significance are listed 

 here: 



I. Actinomyces Harz (1877).— The most widely used generic name 

 for the actinomycetes is Actinoviyces. It gave rise to the etiological des- 

 ignation of the disease actinomycosis, as well as to the name of the order 

 as a whole, Actinomycetales; the common designation of this group of 

 organisms, an actinoviyces or an actinovtycete, has also been derived 

 from this name. It is made up of two Greek words, actino, meaning 

 ray, and myces, meaning fungus. The specific name of the organism 



