770 
Journal of Agricultural Research 
Vol. XXI, No. io 
infusion and incubated. Acid formation in the cresol purple broth is 
indicated by a yellow color. This color was very distinct, and only a 
trace of acid present caused the broth to change from purple to yellow. 
In litmus the results were at times rather indistinct; moreover, the litmus 
was not as sensitive to small amounts of acid as cresol purple. Cresol 
purple was used 50 times in comparison with litmus. Cresol purple gave 
more organisms 14 times; litmus gave higher results 9 times; and equal 
results were obtained 27 times. Hxpressed in percentage, the greater 
number of bacteria were found in the cresol purple solution in 28 per cent 
of the times, in litmus 18 per cent, and in equal numbers 54 per cent. 
Coeon-aEROGENES group.— Bile lactose broth and lactose broth 
were used to determine the number of colon organisms present. Dun¬ 
ham fermentation tubes containing approximately 10 ce. of respective 
media were inoculated with 1 cc. of various dilutions of the silage infu¬ 
sions. The number of organisms present was determined from the 
tube showing gas in the highest dilution. In order to verify the pre¬ 
sumptive test, colon organisms were isolated at different intervals. 
Bile lactose broth and lactose broth were used 55 times in comparison 
with each other. Lactose broth gave more organisms 8 times, bile 
lactose broth gave more 11 times, and equal results were obtained 36 
times. In terms of percentage, lactose broth gave the greater number of 
organisms in 14.6 per cent of the determinations, bile lactose in 20 per 
cent, and equal results were obtained in 65.4 per cent. 
Buugaricus. —The plate method was used to determine the number 
of bulgaricus organisms present. One per cent dextrose agar was 
used to which 1 cc. of a 1 per cent solution of sterile acetic acid was 
added at the time the plates were poured. From time to time organisms 
belonging to the bulgaricus group were isolated and identified. 
Yeast. The dilution method was used to determine the number of 
yeasts present. One per cent dextrose broth in Dunham fermentation 
tubes was inoculated with 1 cc. of the dilutions of silage extract. The 
formation of gas was taken as an indication that yeasts were present. 
This, however, was confirmed by microscopic examination. 
Protein digesters. —Gelatin was inoculated with 1 cc. of the various 
dilutions and incubated at 37° C. The gelatin upon being removed from 
the incubator was placed in a refrigerator. Gelatin which has been 
digested will not solidify upon cooling; hence by taking the highest 
dilution showing liquefaction the number of protein digesters could be 
determined. 
All media used were made according to standard methods and were 
titrated with brom-thymol blue (di-brom-tlrymol-sulplionplitlialein). 
This gave the media a hydrogen concentration of 6.4-7.6 (/) • The \>eriod 
of incubation was seven days at 37 0 C. Direct microscopic counts of 
the silage juice were made with Breed’s method. The results obtained 
compared very favorably with those secured by the plate method. 
