DISTRIBUTION OF STREPTOCOCCI 4I 



(d) Long non- virulent streptococci. 



(c) Long pathogenic streptococci. 



{d) Short highly infectious streptococci. 



Group (d) pertains largely to bacteria which are no longer 

 recognized as streptococci, for example, the diplococcus {Micro- 

 coccus lanccolaiiis) of pneumonia. It is now known that strep- 

 tococci which grow in short chains are often virulent. This is 

 especially true of the pyogenic forms. 



The study of streptococci from various sources, more 

 especially from tissues of diseased animals, suggests the desira- 

 bility of delaying a further classification until more definite 

 data are obtained concerning the natural history, not only of 

 these, but also of the species normally present on the mucous 

 membranes of animals and in nature generally. The specific 

 name is, pathologically or even biologically speaking, of little 

 moment unless we can attach a certain definite meaning to it 

 concerning the morphologic characters, cultural manifestations 

 and the degree of disea.se-producing power possessed by the 

 organism designated. In a group of twenty-eight streptococci 

 previously studied, the writer found the pathogenic forms, 

 i. e. those able to produce disease in rabbits, guinea pigs, or 

 mice, about equally divided between the long and short chains. 

 Of the twenty-eight, nine pos.sessed a certain amount of viru- 

 lence for one or more of these animals. 



§ 21. Distribution of streptococci in nature. The 

 fact has been pointed out in many publications that strepto- 

 cocci are quite widely distributed in nature. The results of 

 the bacteriologic examinations of normal mucous membranes 

 show that they are frequently included in the bacterial flora of 

 the moutli, throat, nares, inte.stines, vagina, and in a few cases 

 they have been found in the bronchioles of the horse and rab- 

 bit They are 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 



