PATHOGENIC BACTERIA. STREPTOCOCCUS PYOGENES. Another organism whose colonies are frequently ob- tained from the pus containing the staphylococci is the Streptococctis pyogenes of Rosenbach (Fig. 53). It was found by him in 18 of 33 cases of suppurative lesions studied, fifteen times alone and five times with the Staphylococcus aureus. It is a spherical organism of.variable size (0.4-1 // in diameter), constantly X FIG. 53.—Streptococcus pyogenes, from the pus taken from an abscess; x looo (Frankel and Pfeiffer). FIG. 54.—Streptococ- cus pyogenes: culture upon agar-agar two days old (Frankel and Pfeif- fer). associated in pairs and chains of from four to twenty in- dividuals. A special variety of it, known as Streptococ- cus longus, sometimes forms chains of more than one hundred members. The organism stains well with ordinary aqueous solu- tions 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 ob- served, and may suggest the thought of arthro-sporulation.