Apr. 12, 1924 
Development of American Foulbrood 
157 
three showed a change from P H =2 to P H =2.8. Therefore apparently Bacillus 
larvae has the ability of producing at least small amounts of ammonia. It seems 
probable that the rather pungent volatile gluelike odor often associated with 
American foulbrood receives some of its characteristics from this ammonia as 
well as from certain of the protein digestion products. 
GELATINE LIQUEFACTION 
The ability of putrefactive bacteria to liquefy gelatin is difficult to demonstrate 
with Bacillus larvae because of the cultural limitations. Maasen states {28) that 
slow liquefication takes place, while White {55) was unable to demonstrate any 
growth in gelatin. The writer inoculated a number of tubes of plain gelatin 
with several strains of Bacillus larvx, all of which showed slight growth, and one 
or two showed a slight softening of the gelatin about the culture growth. Tubes 
of gelatin to which some egg-yolk suspension was added showed this softening 
more markedly, but in no case was there sufficient liquefication to enable one to 
say that it was positive. Decomposed ropy material inoculated into plain 
gelatin, on the other hand, gives a marked liquefaction in a short time. This, 
however, probably is due not to enzyms produced by Bacillus larvae so much as 
to enzyms from the body tissues functioning in the histolysis previous to meta¬ 
morphosis. 
This series of experiments, however, demonstrates that sufficient alkaline 
decomposition products are formed by the action of Bacillus larvae in the prepupa 
to neutralize most of the acid formed by the fermentation of the sugar in the 
intestinal contents and the dextrose resulting from the hydrolysis of the stored 
glycogen. 
DISCUSSION 
PER CENT CONCENTRATION OF SUGAR 
In the data presented it may be seen that there is not an exact correlation be¬ 
tween the percentage of dextrose which inhibits the germination or prevents the 
growth of Bacillus larvae , and the percentage of unassimilated sugar in the larva as 
expressed. The reason for this is that the percentage of unassimilated sugar is 
calculated in relation to the entire weight of the larva, like the figures of Straus 
{43) on the percentage composition of the larva (fig. 15). The percentage of dex¬ 
trose in the culture media gives the actual effective concentration of the sugar in 
the medium by weight. Since the unassimilated sugar is contained almost en¬ 
tirely in the intestine from which it is absorbed, the true concentration of sugar in 
the intestine should be determined in relation to the weight of the intestinal con¬ 
tent. Furthermore, as suggested by Maassen {28), growth of Bacillus larvae 
occurs only inside the intestine until after the histolysis has begun, making pos¬ 
sible the invasion of the body tissues by the organisms. It is therefore in the in¬ 
testinal contents during the last part of the feeding period that the presence of 
sugar is primarily effective in inhibiting the growth of the organisms. The actual 
concentration of sugar in the intestine is, however, difficult to determine accu¬ 
rately, since the actual weight of food consumed by the larva for each 24 hours of 
the feeding period is unknown. Furthermore, the weight of the intestinal content 
is difficult to determine, because of the difficulty of dissecting the intestine free 
from the surrounding body tissues or of removing the contents intact. 
Several attempts were made, however, to remove intestines with as little.adher¬ 
ing tissue as possible from larvse of different sizes during the last two days prior to 
sealing, in order to obtain an approximately accurate figure for the relation be¬ 
tween the weight of the intestine and the weight of the larva. This in the several 
larvse dissected was found to be almost always about 1 to 5. Using this factor, 
