18 



refused to grow at 37 degrees C., at least for a while. In some unpub- 

 lished work the writer has observed that in peptone lactose media at 43 

 degrees C. (in a water bath) all coli culture studied (16) grew luxuriantly, 

 as evidenced by strong turbidity in 24 hours, but 69 percent of these strains 

 showed no gas or only a bubble in this time. Of 20 aerogenes cultures 

 only 2 showed luxuriant growth, 2 a slight growth, while 16 did not grow 

 at all. 



That these two subgroups should show this temperature relationship 

 might be anticipated from a consideration of their respective habitats. The 

 coli section, being most frequently encountered in the animal intestinal 

 tract would naturally have a higher optimum growth temperature than the 

 aerogenes section, which is more characteristic of non-fecal origin. It would 

 be interesting to know whether the members of the aerogenes section, isolated 

 from the intestinal contents of man can be differentiated from the soil 

 and grain strains on the basis of temperature relationship. 



EVIDENCE FROM CARBOHYDRATE METABOLISM 



The metabolism of carbohydrates, particularly glucose, has been care- 

 fully studied by a number of investigators. The work of Harden and Wai- 

 pole on the products of fermentation of glucose; that of Keys and Gillespie, 

 and of Rogers and his associates on the gas ratio; the observations on the 

 Voges Proskauer test and on acid production particularly the recent studies 

 on the limiting H + ion concentration have served to clarify the entire group. 



The Products of Fermentation of Glucose. Harden has prob- 

 ably done the most important and extensive work on this problem. Among 

 the products of glucose fermentation, Harden and Walpole list alcohol, 

 acetic acid, lactic acid, succinic acid, formic acid, carbon dioxide, and 

 hydrogen as indicated in the following table: 



TABLE VII. PRODUCTS OF DECOMPOSITION OF GLUCOSE 

 (After Harden and Walpole 1905-06) 



