386 ANNUAL REPOET SMITHSONIAN INSTITUTION, 193 3 



nomena of cell disruption are dissolution processes of cells that have 

 been exhausted by a period of intensive secretion, during which the 

 secretion products were discharged through the cell walls in the ordi- 

 nary manner. The question can be settled only by more extensive 

 studies from a physiological standpoint. 



Whatever may be the truth concerning the nature of the observed 

 facts of disruption in the stomach cells, it is undoubtedly true that 

 the process is a destructive matter to the cells themselves. Many of 

 them eventually are entirely used up by these activities, and if tliere 

 were no provision for their replacement by new cells the stomach 

 itself would soon be exhausted. The digestive cells are too exclu- 

 sively occupied with secretion duties to be able to reproduce them- 

 selves ; a cell, once exhausted, has reached the end of its career. In 

 examining the section of the stomach (fig. 14), one thing we did 

 not observe is that in addition to the large cells {dg) forming the 

 principal part of the stomach wall, there are other small and incon- 

 spicuous cells {rg) lying outside the others against the inner surface 

 of the basement membrane. These small cells are regenerative cells. 

 They have conserved their vitality by taking no part in the exhaust- 

 ing secretion business, and as a consequence their reproductive pow- 

 ers are unimpaired. When new digestive cells are needed to take 

 the places of those worn out in the service, it is these regenerative 

 cells that by division furnish the recruits. But the parent cell in 

 each case remains behind always ready for further procreation. 

 Thus there goes on throughout the digestive periods of the insect's 

 life a continual process of destruction and regeneration of the cellu- 

 lar lining of the stomach. The regenerative cells may be scattered 

 as shown in the diagram (fig. 14), but in many insects they are col- 

 lected in groups, or nests (called nidi), or again they occur in small 

 pockets of the epithelium (crypts), which may project in the form 

 of slender processes on the outer surface of the stomach. 



At the time that secretion is in progress, or following periods of 

 intensive secretion, the same cells, in most cases, that furnish the 

 secretion products must absorb the digested food materials and pass 

 them through their inner surfaces into the blood of the body cavity. 

 Fortunately, however, the stomach does not have to work all the time. 

 Growing insects, as is well known, have periods when they cease from 

 feeding activities and cast off the outer layer of their skin. This 

 process is called moulting, or ecdysls. The time that intervenes 

 between periods of feeding, when the outer skin is shed, is often 

 spoken of as a " resting period." The appearance of resting, how- 

 ever, is quite superficial, except in the sense that the insect ceases to 

 eat and to move about; physiologically this is a time of greatly 

 increased activity when the processes of growth are particularly 



