Apr. 12, 1924 Development of American Foulbvood 157 



three showed a change from Ph=2 to Ph=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 LIQTJEPACTION 



The ability of putrefactive bacteria to liquefy gelatin is difficult to demonstrate 

 with Bacillus larvae because of the cultural limitations. Maasen states i^8) that 

 slow liqueflcation takes place, while White (SB) was unable to demonstrate any 

 growth in gelatin. The writer inoculated a number of tubes of plain gelatin 

 with several strains of Bacillus larvss, 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 liqueflcation 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 OP 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 

 (45) 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 {^8), 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 larvae of different sizes during the last two days prior to 

 seaUng, 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, 



