INVESTIGATIONS OF ACID ORGANISMS OF MILK. may 
greatest freedom. This was done in order to reduce as low as 
possible the chance of contamination. ‘The tubes were exposed 
to the air only a very few seconds during the milking, and 
were immediately plugged with cotton. Forty-five tubes were 
thus filled and set aside at about 20° C. At the end of 72 
hours 5 tubes had curdled, but were not strongly acid. Plate 
cultures made from them showed that not one of the tubes 
contained 4. acidi lactic’; of the remaining 40 tubes some failed 
to curdle, some curdled with a slightly alkaline reaction, some 
remained neutral, while others became slightly acid, but failed 
to curdle until heated. 
Lixperiment No. 12.,—'The next experiment was designed to 
show, if possible, the actual source of the organism studied. If 
the &. acidt lactict is present in the dust and dirt of the stable 
it ought to be found by direct examination. ‘The experiment 
previously performed of exposing gelatin plates under the flank 
of the cow is unsatisfactory, because the great number of lique- 
fying bacteria prevents a thorough examination of the plates. 
To determine whether #2. acidi lactic’ is present in the dirt a 
large number of test tubes of stevz/e milk were set in various 
places in the barn, and left exposed to the air for 12 hours. 
Hach of these tubes contained about 6 cc. of milk which had 
been carefully sterilized by steam on 3 successive days. ‘The 
opening of each tube measured about 10 millimeters. After 
remaining exposed in the air for 12 hours they were plugged 
and brought to the laboratory and left at a temperature of about 
20°C. In 48 hours every tube had curdled, was strongly acid, 
and had the type of curdling characteristic of B. aczdz lactict. 
As soon as the milk became acid plate cultures were made. 
The B. acidi lactict [/, and B. lactis aerogenes were easily recog- 
nized in these plates, but in this experiment no B. aczdz lactici 
were found. It was, however, thought possible that this organ- 
ism was overlooked because of the presence of rapidly liquefy- 
ing organisms. The characteristic growth of B. aczdt lactice 
only appears after 3 days’ cultivation, and when liquefiers are 
numerous it is impossible to detect the presence of this organ- 
ism. As the liquefiers in the first experiment were quite 
abundant, a second experiment of a similar character, but with 
slight modification, was undertaken. 
