8 
the relation between bacterial multiplication and the formation of 
lactic acid in milk; Burri and Kursteiner^ state that the lactic-acid 
organisms of milk may increase to 100 millions per cubic centimeter 
before there is a definite rise in acidity. The same observation has 
been made by Pennington ^ and associates when investigating the 
decomposition of chicken flesh. In connection with this last study 
it was found that a marked rise in the ammoniacal nitrogen content 
of the flesh did not appear when the bacterial counts indicated a 
few million organisms per gram, but at the next examination, when 
the count was usually in the hundreds of millions, a rise was com- 
monly found. The principles observed by the investigators cited 
are corroborated by the results of the study of bacterial content 
and chemical changes in eggs. 
Not until chemical analyses show rai increase in the ammoniacal 
nitrogen are the senses able to detect infected eggs readily. Studies 
discussed in detail in another section of this bulletin (p. 73) showed 
that sour eggs which in the early stages are, with difficulty, detected 
by the sense of smell, and eggs with light green albumen, which 
are recognized by careful scrutiny, contain bacteria in many millions. 
Eighty commercial samples which contained organisms capable of 
producing gas from lactose in the presence of bile salt were examined 
for B, coll., as described in the chapter on laboratory practice (p. 76). 
A portion from each of the higher dilution fermentation tubes, 
which showed gas, was plated on Endo's medium, or on lactose litmus 
agar, and from each plate having typical coli-like colonies several 
were selected for examination. 
Organisms conforming strictly to the definition for B. coli corn- 
munis^ in the 1905 report of the American Public Health Association 
on Standard Methods of Water Analysis, were isolated from 55 per 
cent of the samples examined. Probably 15 per cent more contained 
organisms which would be classed as typical B. coll by a majority of 
observers because they differed very slightly from the definition just 
given. In the remaining 30 per cent of samples, which were not found 
to contain typical B. coll, the predominating gas-producing organism 
Avas B. (Lactis) aerogenes. Of the typical B, coll organisms ex- 
amined 81 per cent produced gas from sucrose. Practically all of 
the organisms examined would be classed as members of the Colon 
aerogenes group. If gas production from various sugars is sufficient 
to distinguish between varieties of these organisms, a ver}^ large num- 
ber of varieties were isolated. Some of them differed from an}^ at 
present described in the literature. 
iCentralbl. Bakt., 1911, 2. abt, 30: 241. 
2U. S. Dept. Agr., Bureau of Chemistry Cir. 70. 
