100 NUTRITIONAL PHYSIOLOGY 



decomposition of protein is usually confined to the colon. 

 Protein putrefaction is nowadays held accountable for 

 many ailments, and from this view has arisen the common 

 teaching that man would be better off without a large in- 

 testine. Comment upon this opinion may well be re- 

 served for the chapter on the Hygiene of Nutrition. 



The Movements of the Colon. The average rate of 

 progress in the large intestine is low. A factor tending to 

 make it so has recently been brought to notice through the 

 studies of Cannon and others. The ascending colon has a 

 property not duplicated elsewhere in the canal, that of 

 habitual antiperistalsis. As repeated instalments pass the 

 ileocecal valve the cecum is filled and the accumulating 

 contents reach higher and higher levels, but instead of 

 thrusting onward this gathering mass, the circular mus- 

 cular coat most of the time urges it backward. The result 

 is said to be much like what is seen in the antrum of the 

 stomach, although here the direction of the movement is 

 reversed, that is, the waves of contraction press the mix- 

 ture downward into a pouch, from which the only escape 

 is by an eddying reflux through the crawling ring. It is 

 assumed that the ileocecal valve prevents any return to the 

 small intestine. A deliberate hindrance to progress at this 

 point may be of service so far as it secures a more perfect 

 absorption of digestive products and the retrieving of sur- 

 plus water. The antiperistaltic waves are described as 

 starting from a zone in the transverse colon near the mid- 

 line of the body. 



From time to time contractions sweep over the ascending 

 colon in what we should call the normal direction, and send 

 onward more or less of its contents. Beyond the midpoint 

 referred to above those movements which occur are invari- 

 ably progressive, but are separated by long periods of re- 

 pose. If we adopt a recent estimate we can make the fol- 

 lowing general statement: The foremost portion of a meal, 

 that which was first to pass the pylorus and the ileocecal 

 valve, may be expected to be near the spleen at the end of 

 the ninth hour. When defecation occurs all the colon be- 



