MECHANICAL PHENbUENL 3 



opening. KRONECKER and MELTZER believe that the food 

 passes in a spurt from the beginning of the pharynx clear 

 through the oesophagus to the cardiac orifice of the stomach. 

 The contraction of the constrictors of the pharynx and the 

 peristaltic movements of the oesophagus, they believe, follow 

 this act and serve to remove any fragments which may have 

 adhered to the oesophagus. This description we shall see 

 holds only for liquids, and not for more solid foods. They 

 also believe that, in most individuals at least, the food 

 does not immediately enter the stomach but is stopped at 

 the lower end of the oesophagus by a contraction of the 

 circular muscle fibres of the cardia, and is only slowly forced 

 into the stomach by the aftercoming peristaltic wave. The 

 experiments of CANNON and MOSER do not support this view. 



CANNON and MOSER studied the act of deglutition in various 

 animals, including man, by following the passage of liquids, 

 solids, and semi-solids mixed with bismuth subnitrate from 

 the mouth to the stomach by means of the z-rays. The 

 bismuth subnitrate renders the swallowed mass opaque to the 

 x-rays, and as this method necessitates neither anaesthetics, 

 operative procedures, nor recording instruments it is freer 

 from objection than some of the older means employed in the 

 study of deglutition. According to these authors the move- 

 ment of food through the oesophagus differs markedly not 

 only in different animals fcut also in the same animal with 

 food of different consistencies. In fowls, for example, the 

 rate of movement through the oesophagus is always slow, and 

 no matter what the consistency, it is carried from the pharynx 

 into the stomach by peristaltic waves. A squirt-like move- 

 ment when liquids are swallowed is impossible in these ani- 

 mals, as the parts forming the mouth are too rigid- In order 

 to get the swallowed mass within the grasp of the oesophageal 

 musculature the head is raised to aid the weak propulsive 

 powers of the mouth as largely as possible by gravity.. 



In the cat also the food is moved through the oesophagus 

 by peristalsis, but somewhat more rapidly than in th^case 



