20 BULLETIN 433, U. S. DEPAETMEXT OF AGBICULTUBE. 
Organic extractives were determined by subtracting the percent- 
age of ash from that of total solids. The same general changes may 
be noted in this constituent as have previously been noted in case of 
total solids. 
Acidity. — The samples incubated for T. 14, and 21 days, respec- 
tively, show practically no changes in acidity : while the samples in- 
cubated for longer periods show quite marked increases, ranging 
from 1.18 per cent in case of the sample incubated 42 days to 1.8T 
per cent in case of the sample incubated 77 days. It is of interest 
to note that the marked increases in acidity that took place in the 
samples incubated for periods ranging from 28 to 100 days are ac- 
companied by rather marked increases in organic extractives and 
total soluble nitrogen, which would indicate that the acid-forming 
and the proteolytic enzyms were most active at the same time. The 
presence of autolytic acid-forming enzyms in various body tissues is 
well known. (See Inouye. 1908. and Vernon, 1910.) Such enzyms 
produce both volatile and nonvolatile acids, among which are lactic, 
succinic, formic, acetic, and butyric. The action of lactic acid pro- 
ducing enzyms appears to have been studied most extensively. 
Total soluble nitrogen. — This constituent exhibits changes similar 
to those previously noted in case of total solids and organic extrac- 
tives. The sample incubated for 7 days shows a marked decrease in 
soluble nitrogen that amounts to 0.895 per cent : samples incubated for 
14 and 21 days show gradually reduced decreases ; while samples in- 
cubated for periods ranging from 28 to 100 days show gradual in- 
creases in this constituent. It is of interest to note that the decrease 
in soluble nitrogen in the case of the sample incubated 7 days, which 
amounts to 0.895 per cent, is nearly as great as the increase in soluble 
nitrogen in the case of the sample incubated 100 days, which amounts 
to 1.005 per cent. It is apparent that there was at first a rapid de- 
crease in soluble nitrogen, as noted in case of the sample incubated 7 
days, while subsequently the change was in the other direction, 
although in the case of the samples incubated 14 and 21 days the re- 
versal in direction is apparent only when the results are compared 
with those from the sample incubated 7 days. 
The probable causes of these changes will be discussed in connection 
with the nitrogen data in Table 10. 
Coagulable nitrogen. — There is a marked decrease in the coagulable 
nitrogen of the samples as the period of incubation increases. The 
fresh material contains 2.715 per cent coagulable nitrogen, while the 
sample incubated 100 days contains only 0.536 per cent, so that the 
decrease amounts to 2.179 per cent. The causes of these changes will 
be discussed in connection with Table 10. 
Xoncoagulable nitrogen. — The data for noncoagulable nitrogen 
show a fairly regular increase in this constituent throughout the 
course of the experiment, but the rate of increase varies considerably 
