260 APPLIED PHYSIOLOGY 



It must not be supposed that a peristaltic wave 

 traverses the intestine steadily from one end to the 

 other. On the contrary, as it has been graphically put,* 

 the contents * are moved in an irregularly pendulum- 

 like fashion downwards, somewhat like a walker who 

 always takes two steps on and one back, then several 

 forwards, then stands still for some time, and then, as 

 if he had forgotten something, runs back again, but 

 finally, although naturally much later than one who 

 walked right on, he arrives at his goal.' 



The time taken by food to traverse the small in- 

 testine seems to vary considerably. In a patient with 

 a fistula at the lower end of the ileum it was found t 

 that green peas appeared from two and a half to five 

 hours after they had been eaten, and continued to be 

 passed up to the seventeenth hour. Hertz, J as the 

 result of experiments on men in whom the progress of 

 a ' bismuth meal ' was watched by aid of the X-rays, 

 concludes that the average rate at which the contents 

 of the small intestine travel is about 1 inch per minute. 

 Progress through the large intestine is much slower 

 (see Fig. 18). 



Inco- ordination of peristalsis, by which relaxation in 

 front fails to coincide with contraction behind, results 

 in colic. Strong mechanical irritation results often in 

 a local tetanic contraction (enterospasm) and in a peri- 

 staltic wave. Local inflammation of the gut (enteritis) 



* Griitzner, Archwf. d. Ges. Physiol, 1898, Ixxi. 492. 

 f Neucki, MacFadyen, and Sieber, Archiv /. Exper. Path, imd 

 Pharmak., 1891, xxviii. 311. 



| Guy's Hospital Beports, 1907, Ixi. 389. 



