272 BIOLOGICAL PHYSICS 



health, is at least suggestive of their utilisation in the 

 economy of digestion, as a supplement to the many 

 chemical and physical instrumentalities brought to bear 

 on the preparation of the nutritive pabulum, for intestinal 

 absorption and tissue assimilation. 



The larger bowel terminates in what is equivalent to a 

 cloaca, in which, the last chemico-physico-bacterial in- 

 fluences of digestion are brought to bear on the alimentary 

 residuum, in the descending colon, and it seems, to us, 

 more especially anterior to, and in, the sigmoid flexure 

 (Fig. 1 15), which acts as an inner barrier, or valve, to the 

 immediate farther progress of that residuum. We are 

 further of opinion, that this inner anatomical barrier, or 

 valve, is utilised as a pre-anal protective agency against the 

 continuous forward peristaltic movement of the bowel 

 contents, and as a means of prohibiting and preventing 

 peristalsis of the anal portion of the rectum ; peristalsis 

 of which, it seems to us, is produced, or allowed by 

 relaxation of this inner sphincter, and the invasion of the 

 pre-anal gut (Figs. 113, 115), by the faecal contents of the 

 descending colon and sigmoid flexure. The sequence of 

 the phenomena of defecation, moreover, seems to be 

 initiated, in the ordinary physiological conditions of the 

 structures, and their functions, by a continuation of pre- 

 sigmoid peristalsis, along the wall of the pre-anal part of 

 the rectum, which, as the alvine material is passed onward 

 into the lumen of this part of the rectum, reflexly 

 stimulates the systemic nervature of the anal orifice of the 

 bowel, with the result that the anal sphincter is relaxed, 

 and aided, when required, by the voluntary musculature 

 of the abdominal walls, the expulsion of that portion of 

 the excreta, lying between the inner and outer sphincters, 

 is thereby effected. 



It may be that this inner sphincteroid provision, which 

 we have called a faecimeter, is due, largely, to mechanical 

 obstructive circumstances, from flexure alone, but we are 

 disposed to regard it as being aided by anatomico- 

 physiological adjustments and structural adaptation, and 

 that the effect of its operation is the saving of continual 

 discomfort and distress, and the rendering of everyday life 

 experience, not only bearable, but securely safeguarded. 



