i6o Elements of Water Bacteriology. 



all other tests have so far failed. Unlike the colon bacilli, 

 streptococci from the intestines of cattle and men appear 

 to belong to distinct types. The recognition of this fact 

 we owe primarily to Gordon (1905), who made an elabo- 

 rate study of the fermentative power of the streptococci in 

 a long series of carbohydrate media. His work and that 

 of Houston (Houston, 1904; Houston, 1905*; Houston, 

 1905'') have made it clear that the streptococci of the 

 herbivora differ from those found in the human body in 

 their low fermentative power. In a recent review of the 

 genus, Andrewes and Horder (1906) describe the type 

 characteristic of the herbivora under the name, Str, 

 equinus, and define it by its failure to ferment lactose, 

 raffinose, inulin or mannite, or to reduce neutral red. 

 Five other types are described from the human mouth 

 and intestine; all of them ferment lactose, ancf most reduce 

 neutral red and ferment raflSnose. The commonest intes- 

 tinal form clots milk, reduces neutral red and ferments 

 saccharose, salicin, coniferin, and mannite. The specific 

 t3rpes of the genus streptococcus, grade into each other by 

 almost imperceptible degrees, and streptococci fermenting 

 lactose and raffinose and reducing neutral red are some- 

 times found in bovine feces. The fact that Str. equinus 

 is the commonest form among herbivora and a rarer form 

 in man will however prove an important contribution to 

 water bacteriology, if confirmed by other observers. 



The English bacteriologists have ascribed much impor- 

 tance as indicators of sewage pollution to another group 



