128 AIDS TO BACTERIOLOGY 



manifestations may be brought about by the same species. 

 By the injection of a broth culture of Staphylococcus 

 pyogenes aureus into the blood-stream of a rabbit a 

 septicaemia alone is produced, except perhaps in the 

 kidneys, where abscesses may be formed. If, however, 

 before injection the culture is rubbed up with finely- 

 ground potato, abscesses will be produced in the heart 

 and a pyeemic condition be induced, owing to the inability 

 of the potato particles, with the bacteria adherent thereto, 

 to pass through the capillaries. The washing out of a 

 loccilised abscess causing a saprsemia results in an im- 

 provement of the condition of the patient, owing to the 

 removal of organisms producing the offending toxins. 



In addition to the organisms dealt with in this chapter 

 the following are also pyogenic: the tubercle, typhoid, 

 colon, and glanders bacilli, the pneumococcus, the 

 Actinomyces, and certain of the Blastomycetes and 

 Hyphomycetes (q.v.). 



Staphylococcus Pyogenes Aureus. 



Morphology. This organism is a spherical coccus, 

 about 0'75^a to l/u, in diameter, and occurs as a diplococcus, 

 or, more commonly, in grape cluster-like masses. It is 

 non-motile, forms no spores, and is Gram-positive. 



Cultural Characters. The coccus is an ae'robe and a 

 facultative anaerobe. It grows well at room-temperature 

 and at blood-heat. The virulence of cultures persists for 

 many months. In broth a general turbidity forms within 

 eighteen hours. Gelatin begins to liquefy as soon as there 

 is any visible growth, liquefaction occurring in stab culture 

 all along the stab, an orange-yellow sediment being pro- 

 duced. On agar and blood-serum a thick streak develops, 

 which is at first pale, but later becomes golden -yellow; 

 exposure to diffused daylight favours chromogenesis. 



Resistance. The thermal death - point is 58 C. 

 (Sternberg), provided the organism is in a moist con- 

 dition; if desiccated, much greater heat is required. It 

 also seems that certain of the cocci in a culture are more 

 resistant than the majority to destruction by heat and 

 antiseptics. 



Habitat. The surface of the body appears to be the 

 normal habitat; it has been found in dust, earth, and 

 water, but its presence in these is probably accidental. 



