38 



Structure and Classification of Micro-organisms 



There seems, however, no adequate ground for this arrangement, 

 and the old genus Actinomyces should be kept. Eppinger found a 

 streptothrix in the pus of a cerebral abscess, and Petruschky, 

 Berestneff, Flexner, Norris, and Larkin have found streptothrices in 

 cases of pulmonary disease simulating tuberculosis. The organisms 

 described by these writers were not identical, so that there are prob- 

 ably several different species. They usually grow well upon 

 ordinary media and upon solid media form whitish, glistening, well- 

 circumscribed colonies attaining a diameter of several millimeters. 

 As they grow old they turn yellowish or brownish. They liquefy 

 gelatin. Some of the cultures were not harmful to the laboratory 

 animals, others caused suppuration. 



Actinomyces. — The chief characterization of the organisms of this 

 group is a clavate expansion of the terminal ends of radiating fila- 

 ments. These are seen in sections of diseased tissues containing the 

 organisms, but rarely are well shown in the artificial cultures. For 

 further particulars of these organisms see Actinomyces bovis, etc. 



THE YEASTS, OR BLASTOMYCETES 



The organisms of this group are sharply separated from the 

 bacteria by their larger size, elliptic form, and by multiplication by 

 gemmation or budding. 



Fig. 7. — Blastomycetes dermatitidis. Budding forms and mycelial growth 

 from glucose agar. (Irons and Graham, in "Journal of .Infectious Diseases".) 



Each organism is surrounded by a sharply defined, doubly 

 contoured, highly refracting, transparent cellulose envelope. Com- 

 monly each cell contains one or more distinct vacuoles. When 

 multiplication is in progress, smaller and larger buds are formed. 



