THE INFECTIOUS DISEASES. 



205 



not show spontaneous movement, and, like other spheroidal forms, does not appear to 

 develop spores. It is quite tenacious of vitality, surviving long drying and degrees of 

 heut and cold and an exposure to chemical bactericides to which many pathogenic germs 

 readily succumb. It grows well at ordinary room temperature in such artificial culture 

 medi? as nutrient-gelatin, agar, beef tea, and milk, and on potatoes, forming somewhat 

 voluminous masses of culture. It rapidly fluidifies gelatin, 

 coagulates milk, and in the various media develops a yellow- 

 ish-white or a deep golden-yellow color, whence its specific 

 name, aureus, and its common name, "golden coccus." Its 

 color-producing capacity is subject to wide variation. 



FIG. 95. STAPHYLOCOCCUS 



PYOGENES ACREUS. Effects of Staphylococcus Pyogenes m the Body. 



From a beef-tea culture. The virulence of cultures of Staphylococcus pyo- 

 genes obtained from different sources varies con- 

 siderably, but in general, suppuration is not readily induced in the 

 lower animals by its subcutaneous injection. Liability to suppuration 

 is greatly increased by mechanical or chemical injury to the tissues with 

 which the germ is brought in contact. Injection of a virulent culture 

 into the ear vein of the rabbit is usually followed by multiple abscesses 

 in the kidneys and muscles, by suppuration of joints, etc. 



In man this coccus grows readily and rapidly, and may induce necro- 

 sis and exudative inflammation, especially the suppurative phases (Fig. 



FIG. 96. MASSES or MICROCOCCI IN A BLOOD-VESSEL OF THE KIDNEY, INDUCING A SMALL ABSCESS. 

 From a case of pyaemia. 



Around the dilated and partially necrotic blood-vessel in which the bacteria lie is an area of necrotic 

 tissue and a small-celled infiltration or zone of pus. 



96). The lesions which it induces are apt to be circumscribed. It may 

 induce pustules, boils, and abscesses, and A'arious suppurative inflamma- 

 tions of the viscera and serous membranes, joints, bones, endocardium. 



