CONTROL OF THE PUBLIC MILK SUPPLY 449 



of the ratio of carbon dioxid to hydrogen in the gas produced in the fer- 

 mentative reactions that were studied. One of these two groups had a 

 carbon dioxid ratio of 1:1 and was designated as the low-ratio group. 

 The other group had a higher ratio. The correlation of other characters 

 with these types of gas ratio was sufficiently marked to make the separa- 

 tion of the two groups clear and distinct. To determine whether both 

 groups were normal inhabitants of the intestine a study was made of 150 

 cultures from bovine feces. It was found that 149 of them gave the 1:1" 

 ratio which characterized about 50 per cent, of the 120 milk cultures. The 

 single, high-ratio culture was distinguished by a yellow pigment. , The"" 

 fermentative reactions that were studied confirmed the agreefhent be- 

 tween the feces organisms and the low-ratio milk cultures. Further 

 studies showed that the entire low-ratio group is divided into two sub- 

 groups corresponding to B. coli communis and B. coli communior. To 

 determine whether the colon bacillus occurs elsewhere than in the intes- 

 tine a study was made of 166 cultures from 33 samples of common grains. 

 Nearly all of these cultures responded to presumptive tests for B. coif 

 and many would have passed the usual confirmatory tests. On the basis 

 of gas ratio the grain cultures were separable into three groups, viz.: 

 (1) eight of the cultures had the characteristic colon ratio; (2) a group 

 that produced only carbon dioxid and so had a ratio equal to infinity; 

 (3) a group that gave gas ratios varying from 1.90 to 2.90. In the 166 

 cultures a number of pigment formers were noticed and so the cultures 

 were matched with Ridgew"ay's standard color plates whereby it was 

 demonstrated that a larger proportion of the cultures formed pigment to 

 some extent. However, the amount was so small in most cases that the 

 culture would not ordinarily be considered pigmented. Among the de- 

 cidedly colored cultures were all those that gave the colon ratio of 1:1. 

 In all cases the color varied from a cadmium yellow to cream color or 

 nearly white. The 153 cultures that gave a high ratio were divided by 

 the authors into five groups. 



Therefore, the entire collection was divided into six groups; one of 

 them included 40 cultures and another 90, and in these the uniformity of 

 reaction was striking. The number of cultures in the other groups was 

 so small as to make the groups little more than suggestions. 



The authors conclude that the bacteria of the colon type occurring 

 in market milk may be divided into two distinct groups one of which is 

 characterized by a low carbon dioxid ratio that is typical of the colon 

 bacillus of the bovine intestine. The other, or high-ratio group, is 

 numerous in milk but occurs only rarely in the bovine intestine. The 

 surface of dried grains is the source of a number of types of colon' but 

 only one of them resembles the low-ratio feces type and this one is dis- 

 tinguished by its ability to form pigment. Of the cultures from grains 

 the type that is most common probably corresponds to Baet. lactis 



v 



