190 MOUTH DIGESTION. 



solids, as well as of semisolids and liquids, that the experiments 

 of Cannon and Moser were performed". Some of these were on 

 geese, cats, dogs, and horses, and some on man. 



The following is the " summary " of these .later experiments, 

 as published in the American Journal of Physiology : 



" There is a difference in swallowing according to the animal 

 and the food which is used. 



" In fowls the rate is slow and the movement always peri- 

 staltic, without regard to consistency. A squirt-movement with 

 liquids is manifestly impossible, as the parts forming the mouth 

 are too hard and rigid. With this diminution of propulsive 

 power in the mouth there is observed a greater reliance on the 

 force of gravity. The head is raised each time after the mouth 

 is filled, and the fluid by its own weight trickles into the esoph- 

 agus, through which it is carried by peristalsis. 



" In the cat the movement is always peristaltic and slightly 

 faster than in fowls. A bolus takes from nine to twelve seconds 

 in reaching the stomach. Liquids move somewhat more rapidly 

 than semisolids in the upper esophagus. In the lower or diaphrag- 

 matic part the rate is very much slower than above, and is the 

 same for liquids as for solids. 



" In the dog the total time for the descent of the bolus is 

 from four to five seconds. The food is always propelled rapidly 

 in the upper esophagus and moves more slowly below. This 

 rapid movement is frequently continued further with liquid food. 

 No distinct pause was observed when the movement of the bolus 

 changed from the rapid to the slower rate. 



" In man and the horse liquids are propelled deep into the 

 esophagus at a rate of several feet a second by the rapid con- 

 traction of the mylohyoid muscles. Solids and semisolids are 

 slowly carried through the entire esophagus by peristalsis alone." 



The peristalsis of the esophagus is brought about by afferent 

 impulses which reach the center of deglutition and from which 

 efferent impulses pass out to the muscular coat. While the act 

 is, therefore, principally under the control of the nervous system, 

 the stimulation of the successive portions of the mucous membrane 

 as the food passes along may have some part in its production. 



