622 PATHOGENIC MICROORGANISMS 



organisms grew abundantly upon this, but failed to grow on any of the 

 other tissues. After growth of several generations upon this medium, 

 cultures were finally obtained upon agar plates and upon broth. 



Inoculation of cultures into rabbits and guinea-pigs have given rise 

 to subcutaneous abscesses, bronchopneumonia, and suppuration, accord- 

 ing to the mode of infection. 



ACTINOMYCES 



Among the diseases caused by the Trichomycetes or higher bacteria, 

 the most important is actinomycosis. Occurring chiefly in sonie of the 

 domestic animals, notably in cattle, the disease is observed in man with 

 sufiicient frequency to make it of great clinical importance. In cattle 

 the specific microorganism which gives ries to the disease was first 

 observed by Bollinger' in 1877. In the following year Israel^ dis- 

 covered a similar microorganism in human cases. 



The parasites appear in the pus from discharging lesions as small 

 granular bodies, plainly visible to the naked eye and somewhat resem- 

 bling sulphur granules, of a grayish or of a pale yellow color. In size 

 they measure usually a fraction of a millimeter. Ordinarily they are 

 soft and easily crushed under a cover-slip, but occasionally, especially in 

 old lesions, they may be quite hard, owing to calcification. 



Microscopically they are most easily recognized in fresh preparations 

 prepared by crushing the granules upon the slide under a cover-slip and 

 examining them without staining. They may be rendered more clearly 

 visible by the addition of a drop or two of 20 per cent potassium hydrate. 

 When the granules are calcareous, the addition of a drop of concentrated 

 acetic acid will facilitate examination. Fresh preparations may be 

 examined after staining with Gram's stain. Observed under the micro- 

 scope, the granules appear as rosette-like masses, the centers of which 

 are quite opaque and dense, appearing to be made up of a closely meshed 

 network of filaments. Around the margins there are found radially 

 arranged striations which in many cases end in characteristically club- 

 shaped bodies. Inside of the central network there are often seen 

 coccoid or spore-Hke bodies which have been variously interpreted as 

 spores, as degeneration products, and as separate cocci fortuitously 

 found in symbiosis with the actinomyces. Individually considered, 



1 Bollinger, Deutsch. Zeit. f. Thiermed., iii, 1877. 



2 Israel, Virch. Arch., 74, 1878, and 78, 1879. 



