THE ICECHANI8HE OP DIG! 455 



half an hour the contents of both have about the Bame percentage of 

 sugar, but thai for Borne time after this interval the cardiac conto 

 contain considerably more BUgar than the pyloric. Later the percentfl 



of sugar again become aboul equal, qo doubl on a ant of diffusion. 



The diastatic action in the fundus is finally brought to an «ii«l when 

 the contents become completely permeated by the hydrochL "id. 



In this connection it is worthy of note that the addition of hydrochloric 

 acid up to the point of neutrality greatly accelerates the rate of diasti 

 digestion. 



As the outer layers of food in the stomach become partly digested 



account of the action of the pepsin and hydrochloric acid, the f 1 is 



slowly pressed into the active right half of the stomach, \ 

 action of the peristaltic waves it is moved on to the pyloric vestibule. 

 By observing the x-ray shadows east by two pellets of bismuth subni- 

 trate it has been noted by Cannon that, as the peristaltic wave appr 



Fig. 157. — Section of the frozen stomach (rat) some time after* feeding wit:. . ven in three 



differently colored portions. (From Howell's Physiology.) 



a pellet, it causes it to move forward more rapidly tor a Bhort distal 

 but soon overtakes it and in doing bo causes the pellet to move back ji 



little towards the fundus. This backward movement is less than the 

 forward movement, so that after the wave has passed, the position 



the pellet is a little forward of that which it would ha. ipied bad 



there been llo wave. The behavior of the pellet, and. the:'' ' the 



stomach contents, is very like that of a cork floating at the edge of the 

 sea; as each wave approaches, it hurries the cork on a little, but aft 



its passage the cork re les again until the Becond wave carries it still 



a little farther forward. As the peristaltic wave approaches the pyl 

 vestibule and becomes more powerful its effect on the pellets becomes 



more marked. They are carried rapidly along this part of tin eh. 



Until the pylorus is reached. If this remain^ dosed, thej 



into the vestibule. From nine to twelve minutes may elapse tx they 



are transferred to the pylorus from the place where tl • 



by the peristaltic wa 1 



