1324 Wisconsin Academy of Sciences, Arts, and Letters. 
Six fermentation tubes of lactose pep¬ 
tone bile, inoculated with B. coli as 
above • • .... 60%, 55%, 45%, 50%, 50%, 
, Average = 52% 
Six fermentation tubes inoculated as 
above, plus 1 c. c. of sterile milk.. 50%, 55%, 50%, 52%, 55%, 50% 
_. Average = 52 % 
Six fermentation tubes, inoculated as 
above, plus 1 c. c. of raw milk. 65%, 55%, 43%, 58%, 55%, 50% 
Average = 54% 
From these, experiments it seems fair to conclude that the addi¬ 
tion of a small amount of milk to culture media, will not percept¬ 
ibly inhibit the gas production of any B coli contained therein. 
F. Tests for Streptococci. 
Methods for determining the presence of streptococci in millr 
are not satisfactory. A number of laboratories depend upon the 
direct microscopical method. In others the milk is introduced in¬ 
to sugar broth, and after incubation the surface layers are exam¬ 
ined microscopically for long chains. If it were possible to read¬ 
ily and satisfactorily differentiate pyogenic streptococci from the 
lactic acid streptococcus, it would seem likely that a method of 
detection that would be useful would need the following essen¬ 
tials. The culture medium should be selective in the sense of 
favoring the growth of the streptococcus at least equally with any 
other form likely to be present. The resulting growth ought to be 
easily examined microscopically in rather large quantities. Fol¬ 
lowing out these ideas milk was infected with the streptococcus 
and then added, in 1 c. c. lots, to a tube of dextrose broth. This 
culture was grown for 24 hours, and then centrifuged, and the 
sediment examined in a stained microscopical preparation. The 
large amount of curd makes this method useless. It was modi¬ 
fied by straining out, the curd and centrifugating the cleared 
fluid. This was more satisfactory than the first method tried, 
but since it amounted practically to filtering the medium through 
the casein, which would be most likely to hold back the long 
chains, the very elements most sought, this method would be of 
little value. A third step was taken by growing milk in dextrose 
broth as above, and then taking up in a capillary pipette about 
2 c. c. of the upper part of the culture, and centrifugating this 
and examining the sediment. 
In order to thrown down the sediment the milk centrifuge 
tubes of the Stewart-Slack method were used. This method has 
