INSECT'S STOMACH — SNODGRASS 



385 



trated on the one hand by the digestive secretions from the stomach 

 cells, and on the other by the digested products in solution which are 

 to be absorbed by the cells. 



The process of secretion in any gland cell is a chemical activity in 

 the cell protoplasm by which certain sul)stances are produced from 

 the food materials brought to the cell b}' the blood. The nature of 

 the secretion products dilTers according to the function of the gland; 

 the principal products of stomach cells are digestive enzymes. The 

 secretion materials accumulate in the cells until, at tlie proper time, 

 the cell is flushed with water and the products are carried out in 

 solution througli the cell Avail. 



The digestive secretions formed by the epithelial cells of the in- 

 sect's stomach are probably ordinarily discharged through the stri- 

 ated border. In many cases, however, it is to be seen that the inner 



c 



FiGOBE 15. — Diagrams illustrating physical changes that take place In the digestive cells 



of the stomach wall. 



A, cells in a "resting" condition. B, inner ends of cells protruding as swellings 



containing material supposed to include digestive enzymes. C, a swellng disrupted 



scattering its contents in the stomach cavity. D, globules separated from the cells, 

 followed by disintegration. 



ends of the cells have a spongy appearance, owing to the accumula- 

 tion here of a clear liquid containing a coarse granular material, 

 and that small swellings charged with this material push out from 

 the cell surfaces (fig. 15 B). In other parts of the specimen these 

 swellings may be globular outgrowths and some of them may be seen 

 to be rufjtured (C), scattering their contents in the stomach lumen. 

 Or again, the globules may be drawn out on the ends of long necks, 

 and then cut off as free bodies (D), which float oft' and distribute 

 their contents by a final dissolution of their delicate wall. It has 

 usually been supposed that these observed activities in the stomach 

 cells constitute a drastic means for discharging quickly large quanti- 

 ties of digestive products; in other words, it would appear that the 

 ordinary processes of diffusion are too slow, and that more effective 

 results are obtained by an explosive disruption of the cells when once 

 the latter are fully charged with digestive enzymes. Certain recent 

 investigators, however, are inclined to think that these visible phe- 



