SUMMARY 253 



dung and is the commonest form in the air of London. It 

 forms chains of medium length, grows feebly, if at all, 

 at 20 degrees, and ferments saccharose and the glucosides 

 (salicin and coniferin) but not lactose, raffinose, inulin, or 

 mannite. It fails to clot milk or to reduce neutral red. 



Species 2. Str. niitis Andrewes and Horder. 



This type is found most commonly in human saliva and 

 faeces, but is not as a rule associated with disease. It is 

 short -chained, grows well on gelatin at 20 degrees, and 

 acidifies milk without clotting. It ferments lactose as well 

 as saccharose and salicin, but gives a negative reaction to 

 the other tests. 



Species 3. Str. pyogenes Andrewes and Horder. 

 This type represents the highest parasitic development of 

 the group, being rarely found except in association with 

 definite pathological conditions. It occurs in long chains, 

 usually growing in woolly masses at the bottom of a clear 

 broth. It grows well on gelatin at 20 degrees. It is 

 actively hemolytic, but does not form hydrogen sulphid 

 in broth culture. It strongly acidifies milk, but never clots 

 it, nor does it reduce neutral red. The usual positive 

 reactions with Gordon's tests are saccharose, lactose, and 

 salicin. It is highly pathogenic for animals. 



Species 4. Str. salivarius Andrewes and Horder. 

 This type is the commonest form in the mouth, altho 

 it is also found in the intestine. It is a short-chained form 



