155 



A BioMETRic Study of the Streptococci from Milk and from 

 THE Human Throat.* 



By C. M. Hilltard. 



'J'wo hundred and Torty-two pni'c strains of streptococci isolated from 

 milk aud from the luinian tliront liave been compared as to (lieir niorj)]!- 

 ology, Gram stain and i,'entian violet reaction by the plate method, and 

 their quantitative arid production in seven carbohydrate and related or- 

 ganic media. Hemolysis was studied vs'ith f>2 strains. 



We have been able to make no correlation between the length of 

 chain or the relation to violet stain with any other character. 



Seventeen out of 02 cultures gave hemolysis when streaked on blood 

 agar i)lates. Five of these cultures came from normal milk, five — the 

 most vigorous hemolizers — were from milk where udder trouble was indi- 

 cated in the cow, aud seven A^ere normal throat forms. 



The seven substances tested showed a definite order of availability 

 for acid produrtion. This order ("metabolic gradient") and the per cent. 

 of cultures yielding 1.2% or more of acid when grown at 37 C for three 

 days is shown in the following table : 



Gluecose (Monosaccharide) 08.0% 



Lactose (Disaccaride) 76.0% 



Saccharose (Disaccharide) 6.5.5% 



Salicin (Glucoside) 42.7% 



Kaflinose (Trisaccharide) 37.. 5% 



Inulin (Starch) 9.0% 



Mannite (Hexahydi'ic alcohol) 1.5% 



It will be noted that the degree of availaliility is closely associated 

 with the size and complexity of the substance. 



According to the positive reaction — over 1.2%, acid — in the test sub- 

 stances, 88% of the cultures inay bo placed in eight groups. 



The following features separate milk from throat streptococci : 

 (1) Milk organisms yield over 2.5% acid in lactose and saccharose at 

 37 C. (2) They seldom ferment a substance higher in the metabolic series 



*Full Report in Jour. Ind. Dis. Vol. XII, No. 2. 



