368 



C. M. Child 



Under extreme conditions of intestinal distension with material 

 all parts may be subjected to equal or nearly equal internal pres- 

 sure but when decrease m the amount of intestinal contents occurs, 

 as is the case when the animals are kept without food, 

 the energy of the mechanical conditions connected with 

 the contents must decrease more rapidly in the periph- 

 eral than in the middle regions. Thus, for example, 

 if the intestine is only partly filled, the internal pressure 

 on the walls in the extreme anterior and posterior regions 

 is in general much less than in regions nearer the middle. 

 In the first place, the fluid contents are forced into this 

 region only during extreme extension and then appar- 

 ently with much less energy than into regions nearer 

 the middle. The consequence is that those regions 

 in which the functional stimulus falls below a certain 

 minimum gradually undergo atrophy and degeneration, 

 and as the intestinal contents continue to decrease in 

 amount this atrophy and degeneration gradually extend 

 toward the middle region, which is the last to be 

 affected. 



Size of the lumen of the various parts and friction 

 between the contents and the walls must also play a part 

 in determining movements and internal pressures of the 

 intestinal contents and both of these factors tend to 

 reduce the energy of the functional conditions more 

 rapidly in the peripheral than in the middle regions. 



The lateral intestinal branches in and about the 

 pharyngeal region persist longer than any others, simply 

 because the functional conditions are less altered there 

 than elsewhere. In the first place, contraction which 

 drives the intestinal contents toward the middle is usu- 

 ally sudden and violent, in consequence of sudden ex- 

 ternal stimuli, while extension is usually much slower 

 and less extreme. Consequently the intestinal contents are 

 driven into the lateral branches of the middle regions with great 

 force long after they have ceased to reach the extreme peripheral 

 regions at all. The normal movements of the animal, especially 



Fig. 6 



