42 STREPTOCOCCI 



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 considered as accidental or secondary invaders, although 

 in some of these maladies, such as tuberculosis, they are be- 

 lieved to be of more or less secondary importance. When, how- 

 ever, the specific cause of the disease is not positively known, 

 and streptococci which possess certain pathogenic powers for 

 experimental animals are constantly present and seem to 

 stand in a causal relation to the disease, the pathologist is 

 confronted with a puzzling problem in trying to determine the 

 source and the etiological importance of the organism in hand. 

 In cases of infection leading at once to septicemia, peritonitis 

 or suppuration, the explanation is more simple than in the 

 epizootic diseases, such as Bnisiseuche, where the constant 

 presence of streptococci in the lesions can be quite as easily 

 explained on the ground of their invasion of the parts affected 

 from a normal habitat as on the hypothesis of a specific in- 

 fection. It is in these instances that we are seeking for the 

 crucial test. 



We have found in a few test experiments that when cer- 

 tain of the delicate streptococci which exist (are foundj in ex- 

 ternal nature (soil or water) are introduced within the tissues 

 of certain animals they become, by reason of their activities, a 

 source of irritation which causes local tissue disturbances. In 

 a few cases they have produced septicemia with fatal results. 



In cases of infection resulting in septicemia, or in those 

 where the disease is more localized, as in strangles or mastitis, 

 and possibly in others where the affection spreads more or less 

 rapidly, we cannot well escape from the feeling that the strep- 

 tococci, present in such large numbers, must either stand in a 

 causal relation to the disease or be accounted for bv their 



