GENUS STREPTOCOCCUS 193 



and forms sulphuretted hydrogen in broth cultures. It has no 

 hemolytic power and little virulence, but produces a positive 

 reaction to all of Gordon's tests except raffinose and inulin. 

 That is, it clots milk, reduces neutral red, and ferments sac- 

 charose, lactose, salicin, coniferin, and mannite. The mannite 

 reaction is specially characteristic of this intestinal type. 



7. Streptococcus gracilis (Escherich, Lehmann and Neu- 

 mann). Small coccus occuring in chains. Ferments lactose 

 and coagulates milk. May ferment salicin and mannite. 

 Liquefies gelatin, actively. 



It is evident that a natural and acceptable classification 

 of streptococci has not been made and probably can not be 

 until further facts concerning them are known. 



Distribution of streptococci. It has been pointed out in 

 many publications that streptococci are quite widely distrib- 

 uted in nature. The results of the bacteriologic examinations 

 of normal mucous membranes show that they are frequently 

 included in the bacterial flora of the mouth, throat, nares, in- 

 testines, vagina, and in a few cases they have been found in 

 the bronchioles of the horse and rabbit. They art; also present 

 in greater or less numbers on the skin, especially in the deeper 

 layers, presumably in the ducts of the sweat and sebaceous 

 glands and along the hair shafts and follicles. They exist in 

 soil and in water, and occasionally these forms are quite as 

 delicate in their morphology and equally as sensitive to the 

 influence of environment as those isolated from normal or 

 diseased animal tissues. In view of this wide distribution, the 

 presence of a streptococcus in any abnormal condition can not 

 be considered necessarily a specific infection from a previous 

 case of the same kind. In many affections where the specific 

 organism has been demonstrated, such for example as diph- 

 theria and tuberculosis, streptococci frequently appear in the 

 lesions. In these cases, they are considered as accidental in- 

 vaders, although in some of these maladies, such as tubercu- 

 losis, they are believed to be of more or less secondary im- 

 portance. When, however, the specific cause of the disease is 

 not positively known, and streptococci which possess certain 



