30 STREPTOCOCCI IN NATURE 



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 espe- 

 cially from tissues of diseased animals, suggests the desirability 

 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 generalh'. The specific name is, 

 pathologically or even biologically speaking, of little moment 

 unless we can attach a certain definite meaning to it concern- 

 ing the morphologic characters, cultural manifestations and the 

 degree of disease-producing power possessed by the organism 

 designated. In a group of twenty-eight streptococci previ- 

 ously studied, the writer found the pathogenic forms, /. e. , those 

 able to produce disease in rabbits, guinea pigs, or mice, about 

 equally divided between the long and the short chains. Of 

 the twenty-eight, nine possessed a certain amount of virulence 

 for one or more of these animals. 



§ 20. 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 mouth, throat, nares, intestines, 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. The}' 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 diseased animal tissues. In view of this wide 

 distribution, the presence of a streptococcus in any abnormal 

 condition cannot 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 diphtheria, tuberculosis, and hog cholera, strepto- 

 cocci frequently appear in the lesions. In these cases, they are 



