26 PHYSIOLOGY OF ALIMENTATION. 



more than half an hour, during all of which time the form 

 scarcely changes its position in the abdomen. In one 

 instance the segmentation was seen to continue with only 

 three short periods of inactivity for two hours and twenty 

 minutes. 



The above description holds for the usual movements of 

 the small intestine, and when the food is not too thickly 

 crowded in that region of the gut. When too large an 

 amount of food is present in any given portion of the in- 



v, ^ w w w ^/-r ^B 

 2~\ (^~~^) <^S r~^ /^\ *y 



FIG. 5. 



(Copied from CANNON: American Journal of Physiology, 1902, 

 VI, p. 256.) 



testine the constrictions may not completely divide the 

 string of food, but only in part. This condition of affairs 

 is illustrated in line 1 of Fig. 6. 



Furthermore, the constrictions do not always take place 

 in the middle of a segment, but more toward one side of it, 

 as indicated by the dotted divisions in line 1 of Fig. 6. In 

 this way one-third of each segment may be pinched off at 

 each division, and only every third segmentation restores 

 the original order of the series. Thus, in Fig. 6, the first 

 division occurs along the dotted line a in each segment. 

 This brings about the state of affairs shown in line 2. In 

 this series the fragment of food at the extreme right of the 

 string consists of one-third of an original segment, while that 

 at the extreme left consists of about two-thirds of a segment. 

 The next division which takes place along the dotted 

 line b brings about the condition of affairs indicated in line 



