THE ACTINOMYCETES, Vol. I 



(1929) proposed that this isolate be named 

 Actinomyces graminis. Vuillemin (1931) con- 

 sidered it to be identical with Actinomyces 

 sulphureus Gasperini (1894). 



In the absence of pure cultures of the 

 causative agent of the disease for compara- 

 tive studies, some of the early workers on 

 actinomycetes had only a limited concept of 

 the growth and life cycle of these organisms. 

 This is illustrated, for example, in the de- 

 scription by MacFayden (1889) of the his- 

 tory of an actinomycete colony: 



"It has its starting point in one or more 

 cocci transported by the plasma currents or 

 by the agency of a carrier cell (leucocyte). 

 The cocci multiply by elongation and subse- 

 ciuent fission. By elongation some of the cocci 

 give rise directly to short bacillary forms, 

 and through these to long filaments. The 

 further extension of the colony is effected by 

 the growth and multiplication of both 

 threads and cocci. The majority of the 

 threads tend to develop clubs at their outer 

 ends (involution forms)." For more phan- 

 tasy and inaccuracy, one would have to 

 search widely in microbiological literature. 



Not much progress in the general under- 

 standing of these organisms seems to have 

 l)een made during the next 20 years, as illus- 

 trated by reference to them in the Second 

 Edition of H. W. Conn's (1909) Agricultural 

 Bacteriology. In speaking of the actinomy- 

 cetes, he says: 



"Under this head are included a few forms 

 of fungi which resemble other bacteria in 

 some respects, but differ in others. They are 

 composed of threads which are commonly 

 larger than the threads of bacteria, and 

 which may show freciuent branching, a char- 

 acteristic not usual in bacteria. They also 

 ha\'e a peculiar method of forming reproduc- 

 ing l)odies. The group is not one of xevy great 

 importance. One type of Streptothrix is ex- 

 tremely abundant in soil and appears as 

 round, white opac^ue colonies with an exten- 

 sive brown halo upon the plates." 



An important cause of confusion was the 

 fact that the actinomycetes were grown on 

 nitrogen rich organic media, now known to 

 be totally unsuitable for them to form a char- 

 acteristic growth, essential for comparative 

 studies and for proper identification. As a 

 result, a highly complex terminology was 

 developed for the designation of actinomy- 

 cetes; numerous descriptions of "new" spe- 

 cies soon began to appear. This is illustrated 

 by the summary made, as early as 1892 to 

 1894, by Gasperini (Table 1). There is no 

 wonder, therefore, that the nature and classi- 

 fication of the actinomycetes soon appeared 

 hopeless. 



The adoption of the name "actinomy- 

 cetes" was suggested by Gasperini and Lach- 

 ner-Sandoval. Sanfelice, impressed by the 

 analogy of the biological properties of the 

 actinomycetes and those of the tuberculosis 

 organism, suggested that the relationship of 

 the actinomycetes to the bacteria was closer 

 than to the fungi. Gasperini emphasized that 

 the species or varieties belonging to the ac- 

 tinomycetes, included under one genus Ac- 

 tinomyces, show great variations in form and 

 in behavior, especially in their ability to 

 produce aerial spores and soluble pigments. 

 Some of these properties were recognized to 

 be inconstant and were found to depend on 

 the conditions of culture and the composition 

 of the medium; minor variations of the latter 

 could bring about marked changes in growth 

 and pigmentation. 



Historical Periods 



Before we consider in detail the historical 

 backgroimd of our knowledge of the actino- 

 mycetes, we must recognize certain distinct 

 periods in which the ^'arious concepts con- 

 cerning the nature of these organisms and 

 their importance in the cj^cle of life became 

 crystallized. There is, of coiu'se, considerable 

 ()\erlapping of the \-arious periods, since no 

 one period came to an end ])efore another 



