Abstract
The pH of the intestinal juice of the 5th instar larvae of Bombyx mori after being starved for one day is ca. 9.8.
Proteases, both from the intestinal juice and from the glycerin extract of the intestinal epithelium, have the same optimal pH of 9.5. With the gliadin only, it is ca. 10. The protease can digest both vegetable and animal proteins and peptone.
The digestion of glycylglycin occurs only with glycerin extract of the epithelium, and its optimal pH is ca. 8.
Amylase has its pH optimum at 9.5; maltase, at 6.8; and invertase, at 7.0. The composite optimum of amylase and maltase (the saccharogenesis by the crude intestinal juice) is 8.0. Cellulase and Zytase are absent.
Disaccharide ferments are, as is the case with dipeptide ferment, localized to an extent in the intestinal epithelium.
The most interesting and important thing is that the depolymerisation of the food materials (protein, starch) begins within the intestinal lumen by the juice secreted therein and goes on most favourably at the natural pH (9.5) of the juice, whereas the final disintegration of the end products of the above, so to speak, preliminary digestion (dipeptides, disaccharides) occurs rather exclusively within the epithelial cells and at more or less neutral reaction on their way from the lumen to the circulatory system.
