Dr Barclay-Smith, Extreme Visceral Dislocation. 21 



viz. of the ascending and transverse colons, were usually of a 

 character quite distinct from those involving the small intestine 

 and the distal part of the large gut. These movements were of 

 the nature of an anti-peristalsis which exhibited a certain rhythm, 

 and was remarkably constant. The effect of these anti-peristaltic 

 waves was to cause an accumulation of the intestinal contents in 

 the proximal part of the large intestine and a prolonged arrest of 

 their progress. 



This mechanism seems to be brought into play when the 

 contents of the small intestine pass into the large, and become 

 more pronounced as the accumulation increases. He states that 

 the ileocolic valve is to be regarded as normally competent, and 

 consequently the anti-peristaltic contraction does not bring about 

 an escape of the contents of the large intestine into the small. 

 Though Cannon seems to prove fairly conclusively that this anti- 

 peristaltic wave is a constant and normal feature of the intestinal 

 mechanism, he makes no suggestion as to its physiological meaning. 



It probably, however, throws valuable light on the interpretation 

 of the ileocolic valve and the mechanism whereby a well developed 

 csecum is of functional importance as an appendage to the gut. It 

 has always been a problem why an enormously long csecal append- 

 age, such as is found in a typical herbivorous mammal, should be 

 found distended with semi-digested contents, why the csecal tube 

 should apparently prove the path of least resistance, and why the 

 intestinal contents should not take preferentially the continuous 

 route via the large gut. 



It is certainly open to surmise that the anti-peristaltic wave is 

 a pronounced feature in the intestinal mechanism ; that its object 

 is to fill the csecal diverticulum and that the ileocolic valve is an 

 arrangement whereby the anti-peristalsis will not bring about 

 regurgitation into the small intestine. 



One feature of Cannon's results is at first sight remarkable, 

 viz. that he should have found such clear evidence of this anti- 

 peristaltic wave in the cat, an animal carnivorous in diet and with 

 but slight csecal development. This however may be a fulfilment 

 of the general law that physiological function once established, 

 it proves remarkably stable ; in this respect presenting a great 

 contrast to anatomical features which may be trimmed to an 

 indefinite extent to meet the necessities of the race. 



These premises being granted, the adaptation of an ileocolic 

 valve, and the interpretation of a csecal diverticulum now become 

 intelligible. 



The differentiation of a so-called large or distal from a small 

 or proximal gut is established at a very early evolutionary stage, 

 and this differentiation is usually in the form of a valvular arrange- 

 ment. 



