SUPPURATION. 



157 



generally does not contain the Staphylococcus aureus 

 alone, but. shows colonies of the Staphylococcus albus as 

 well. In addition to these two principal forms, one 

 sometimes discovers an organism identical with the pre- 

 ceding, except that its growth on agar-agar and potato 

 is of a brilliant lemon-yellow color, and its pathogeny for 

 animals much less. This is the Staphylococcus citreus of 

 Passet. It is not quite so common, and not so patho- 

 genic as the others, and consequently much less important. 



Another organism whose colonies are, frequently ob- 

 tained from the pus containing the staphylococci is the 

 Streptococcus pyogenes of Rosenbach (Fig. 47). It was 

 found by him in 18 of 33 cases studied, 

 fifteen times alone and five times 

 with the Staphylococcus aureus. It 

 is a spherical organism of variable 

 size (0.4-1 fi. in diameter), constantly 

 associated in pairs and chains of from 

 four to twenty individuals. 



The organism stains well with or- 

 dinary aqueous solutions of the anilin 

 dyes, and also by Gram's method. 

 Like the coccus already described, it 

 is not motile and does not seem to 

 form spores, though sometimes a large 

 individual much larger than the 

 others in its chain may be observed, 

 and may suggest the thought of arthro- 

 sporulation. 



Upon gelatin plates very small col- 

 onies of translucent appearance are 

 observed. When superficial, they 

 spread out to form flat disks about 

 o. 5 mm. in diameter. The microscope 

 shows them to be irregular and gran- 

 ular, to have a slightly yellowish color, 

 and to have numerous irregularities around the edges, due 

 to projecting chains of the cocci. No liquefaction occurs. 



FIG. 48. Streptococ- 

 cus pyogenes : culture 

 upon agar-agar two days 

 old (Frankel and Pfeif- 

 fer). 



