306 THE STREPTOCOCCUS-PNEUMOCOCCUS GROUP 
substance is rather firmly bound to the organisms and does not appear 
in the medium to any considerable degree. M'Leod/ M'Leod and 
M'Nee,^ and LyalP have studied the conditions favoring the forma- 
tion of the hemolysin and find that sugar-free ascitic broth is suitable 
for this purpose. Utilizable sugars prevent the formation of the 
hemolysin. The substance is thermolabile and is found in an active 
state only during the first twelve or twenty-four hours of culture, 
at which time small amounts of sterile (filtered) broths, 0.01 to 0.1 
cc. are strongly hemolytic. The hemolysin does not induce antibody 
formation when it is injected into susceptible animals. Hemoglobin- 
emia and hemoglobinurea are produced in rabbits that are very sus- 
ceptible to the hemolysin; less susceptible rabbits react but slightly. 
There is no definite evidence that streptocolysin plays a prominent 
part in the streptococcus infections of man. Virulence and hemo- 
lytic activity are frquently, but by no means necessarily, parallel 
phenomena. Recent observations by Davis'* and Otteraaen^ upon the 
prevalence of hemolytic streptococci in the throats of normal indi- 
viduals and those suffering from acute diseases indicate that hemolytic 
streptococci are frequent inhabitants. The strains isolated were not 
virulent, as indicated by the results of animal inoculation. 
Distribution in Nature.— Streptococci are widely distributed in 
nature, always, however, in rather intimate association with man 
or the higher animals. They are found in the soil, water, milk and 
they exist as "opportunists" on the exposed surfaces and mucous 
membranes of man. They are common in the mouth, nose and 
throat, the intestinal tract, and rare in the normal vagina. 
Pathogenesis.— //?/?» a??.— Streptococci excite both local inflamma- 
tory and suppurative processes and generalized septicemic infections, 
the latter being the more common and characteristic. They are 
found in the throat, and occasionally the blood, of scarlet fever cases, 
and recent work indicates that they are the etiological factor in this 
disease.^ Superficial lesions incited by streptococci may be mild in 
character, resembling those caused by staphylococci. The organisms 
may, and frequently do, enter the blood or lymph channels, and spread 
rapidly through the body, inciting the most severe generalized infec- 
tions. Streptococci were also the causative agents in the very severe 
streptococcus pneumonias which were epidemic in the cantonments of 
the American Army in 1917.'^ Streptococci are the etiological agents 
of erysipelas, frequently of general and puerperal sepsis and phlebitis, 
and inflammations of the internal organs; of these, the middle ear, 
the endocardium, the peritoneum, the meninges or joints are more 
1 Jour. Pathol, and Bacteriol., 1912, 16, 321. 
2 Ibid., 1913, 17, 524. 
3 .Jour. Med. Res., 1914, 30, 487. 
^ Illinois Med. Jour., September, 1919. 
^ Jour. Infec. Dis., 1920, 26, 23. 
6 See Scarlet Fever, page 314. 
' Jour. Am.' Med. Assn., 1918, 71, 443. 
