STREPTOCOCCI IN NATURE 3I 



considered as accidental or secondary invaders, although in 

 some of these maladies, such as tuberculosis, they are believed 

 to be of more or less secondary importance. When, however, 

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

 streptococci which possess certain pathogenic powers for ex- 

 perimental 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 septicaemia, peritonitis or suppura- 

 tion, the explanation is more simple than in the epizootic dis- 

 eases, such as Brustseuche , where the constant presence of strep- 

 tococci 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 infection. It is in 

 these instances that we are seeking for the crucial test. 



We have found in a few test experiments that when certain 

 of the delicate streptococci which exist (are found) in external 

 nature (soil or water) are introduced within the tissues of cer- 

 tain animals they become, by reason of their activities, a source 

 of irritation which causes local tissue disturbances. In a few 

 cases they have produced septicaemia with fatal results. 



In cases of infection resulting in septicaemia, 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 bj^ their rapid 

 proliferation in native soil made favorable for their excessive 

 increase by the conditions produced by the true etiological fac- 

 tors. Their natural distribution is so wide, and their virulence 

 so capricious that a secondary invasion, which seems always to 

 be possible, renders the fixing of etiological responsibility upon 

 a streptococcus isolated from any diseased tissue a somewhat 

 difficult task. The problems in this connection which concern 

 us most and which need more extended investigation pertain 

 (i) to the determination of the parasitic possibilities of strepto- 

 cocci existing in nature /. e., those ordinarily considered as sap- 



