THE INFECTIOUS DISEASES. 207 



of streptococci are dense and compact. Not infrequently the growth is diffused through 

 the nutrient broth, rendering it turbid. When in vigorous growth it coagulates milk. 

 Streptococcus, as well as Staphylococcus pyogenes aureus, develops haemolytic sub- 

 stances in its growth. 1 



There is considerable difference in the tenacity with which, in broth cultures of 

 streptococci from different sources, the individual cocci cling together, so that in one set 

 of cultures the chains may be very long, in another short. It has been thought by some 

 observers that this difference is so constant as to justify special names for these growth 

 variants of the streptococcus, a*nd they have been called respectively Streptococcus longus 

 and Streptococcus brevis. The growth in small dense masses has given rise to the name 

 Streptococcus conglomeratus. It is doubtful whether these names indicate more than 

 f\. * *" t< ^ rather inconstant growth varieties depending upon 



t* ? *5 V^***3* variations in the culture media. 

 * ^Qa&A/y.i Effects of Streptococcus Pyogenes in the 



Body. Streptococci which give evidence of 

 little virulence in animal inoculation are very 

 common in the mouths of healthy persons. 

 The significance of these germs in healthy 



mouths is not yet clear. 



FIG. 97. STREPTOCOCCUS PTOGEXES. 



From a broth culture. The results of animal inoculation with the 



Streptococcus pyogenes are in general simi- 

 lar to those with the Staphylococcus pyogeues aureus. The strepto- 

 coccus is very frequently associated with the Staphylococcus both in its 

 distribution outside the body, in healthy persons, and in disease. In 

 general it may be said that the streptococcus incites those forms of sup- 

 puration and fibriuo-purulent inflammation which tend to spread both 

 locally and through metastasis. 



Streptococcus pyogeues has been found either alone or in association 

 with Staphylococcus in a large number of suppurative processes in vari- 

 ous parts of the body, the condition in some cases receiving special names, 

 in others not. Thus in boils and carbuncles, in abscesses and phlegmons, 

 in herpes, impetigo and panaritium, in phlebitis and lymphangitis, in 

 erysipelas, in suppurative inflammation of various mucous and serous 

 membranes, and in some forms of pneumonia, one or other or both of 

 these germs are frequently concerned. 2 



One of the most important features of the relationship of Streptococ- 

 cus pyogenes to man is the frequency with which it enters as a concur- 

 rent pathogenic agent in already established infectious diseases due to 

 other forms of micro-organisms. Thus some of the most serious com- 

 plications to which the victims of scarlatina, diphtheria, typhoid fever, , 

 and pulmonary tuberculosis are liable are due to the action of the strep- 

 tococcus in the body rendered unusually vulnerable by the existence of 

 another form of infection. The serum of individuals adapted (immu- 

 nized) to streptococci may agglutinate the micro-organisms. 3 



Streptococci which upon their isolation from the body in suppurative or other in- 

 fectious processes are very virulent, usually, and sometimes very quickly, partially or 



1 For haemolysis of streptococcus, see Schelsinger, Zeit. f. Hyg. u. Infkr., Bd xliv., 

 1903, p. 428. 



- Anaerobic streptococci have been found by various observers in abscesses and 

 other forms of suppuration of which they are apparently the excitants. 



3 For a study of agglutination of streptococci see Jfoser and Clemens, Centrbl. f. Bak., 

 Abth. I., 1903, pp. 560 and 714; also SenfeM, Zeitsch. f. Hyg. u. Infkr., Bd. xliv., 

 1903, p. 161; also, Weaver, Jour, of Inf. Dis., vol. i., 1903, p. 91. * 



