206 THE INFECTIOUS DISEASES. 



etc. These effects may be induced by the staphylococcus alone or by 

 it in association with other species of germs. 



Staphylococcus pyogenes aureus incites these changes iii the body in 

 virtue of certain toxins or toxalbumins which are produced as the re- 

 sult of its metabolism, and which are either at once set free or stored up 

 in the body of the germs until their release by disintegration after the 

 death of the germs. The special power of the staphylococcus to cause 

 the gathering of leucocytes is apparently due to the marked chemotactic 

 powers of some of the proteid substances in its protoplasm. 



It may enter the body through wounds, small or large, of the skin 

 or mucous membranes, and sometimes through uninjured surfaces. In 

 many cases its mode of access is not evident. ' While usually this germ 

 soon dies in the body, it may remain for a long time alive. 



It is widespread in inhabited regions, especially in towns, being fre- 

 quently found on the surface of the body, and in the saliva, particularly 

 of those with acute or chronic catarrh of the upper air passages. As the 

 result of the filthy habit of indiscriminate public spitting, it is common 

 in the dust of hospitals, houses, towns, public conveyances, and places 

 of public assembly. 2 



Other Forms of Staphylococcus. 



Staphylococcus pyogenes albus. This appears to be a variety of the Staphylococcus 

 pyogenes which does not develop the yellow color in cultures. It is of frequent oc- 

 currence both in connection with the aureus and alone. Its action on the body is similar, 

 but it has seemed to many observers to be in general less virulent. 



Staphylococcus epidermidis albus. This coccus has been described by Welch as of 

 frequent occurrence in the epidermis, and although of rather feeble pyogenic power, 

 yet seems frequently to cause small stitch-abscesses and moderate suppuration along 

 drainage tubes. Welch regards it as possibly a variety of Staphylococcus pyogenes 

 albus. 



Other forms of staphylococcus have been described S. salivarius pyogenes, S. 

 cereus albus and flavus but they are apparently of little pathological significance. 



CHARACTERS OF THE STREPTOCOCCUS PYOGENES. 



The Streptococcus pyogenes (Micrococcus pyogenes) is distinguished morphologically 

 from the cocci just described by the marked tendency which the individuals exhibit, 

 when growing, to hang together in longer or shorter chains (Fig. 97). It is like the 

 Staphylococcus pyogenes, immobile, and stains easily in the same way. By a special 

 method Hiss has demonstrated a capsule on streptococci. 3 



It grows readily, but more slowly than Staphylococcus pyogenes, on the ordinary 

 culture media. It does not fluidify gelatin, on which it grows as small, inconspicuous, 

 grayish-white colonies. On the surface of agar plates kept in the thermostat at 37 C. 

 for twenty-four hours, the small grayish colonies usually show, under the microscope, 

 loops and fringes of the chain-like cocci extending off from the borders. The growth on 

 potatoes is inconspicuous. In nutrient broth it usually forms delicate, flocculent masses, 

 which cling to the sides of the tubes, leaving the fluid clear. Occasionally the masses 



1 For a resume of the role of S. pyogenes aureus in the skin disease, with bibliogra- 

 phy, see White, Boston Medical and Surgical Journal, vol. cxli., p. 235, 1899. 



2 For bibliography of S. pyogenes aureus, consult article by Neisser and Lipstein in 

 Kolle and Wasserman'n's "Handbuch der Mikroorganismen," Bd. ii., p. 105. 



3 Hiss, Science, March 7th, 1902, p. 367, preliminary communication. 



