Apr. 12, 1924 



Development of American Foulbrood 



161 



feeding has ceased and the sugar-containing food has largely been assimilated, 

 because, with the rate at which the larva is given food containing about 14 per 

 cent sugar, the sugar concentration in the intestine must rapidly increase beyond 

 the 3 to 4 per cent concentration which inhibits growth, so as to prevent the 

 development of the disease in the larva. From Tables IX and X it may be seen 

 that from the second day on, increasing numbers of visits are made to the larva 

 with an increasing amount of time spent in nursing (Table X), so that on the 

 last day of feeding a nursing visit, averaging six seconds in duration, is made 

 approximately every 30 seconds, or an average total during the last 24 hours of 

 2,855 visits, or 36 per cent of the average 7,858 visits made during the entire 

 feeding period (Table IX). The rapid consumption of this great amount of 

 food, which is supplied in almost a steady stream, is indicated by the fact that 

 the amount of food in the cell with the larva decreases to less than 10 per cent 

 of the weight of the larva just prior to sealing. Even though the exact amount of 

 food consumed may not be known, the actual concentration of sugar in the 

 intestine during this period must rapidly rise, because of the high concen- 

 tration of sugar in the food and the volume at which it apparently is fed to the 

 larva, to several times the concentration necessary to inhibit the growth of 

 Bacillus larvae. There is, as mentioned above, a diluting factor due to the 

 accumulation of undigestible material until the connection is made with the 

 end intestine, but, as shown by the microscopical examination of the intestinal 

 contents, this, because it is largely insoluble, is probably of relatively slight 

 importance in its effect upon the actual sugar concentration in the intestine 

 during the period when inhibition occurs. 



Table IX. — Relation of nursing to increase in weight of larva "■ 



" From Sturtevant (SJ) and Linehurg (2S). 



Table X. — Time spent in feeding " 



" Calculated from Lineburg {IS). 



