DEGLUTITION. 35 



passage of the food and drink from the pharynx, by the gullet, 

 into the stomach. 



60. The pharynx (Fig. 31) is the cavity immediately fol- 

 lowing the mouth, and communicating with it hy the isthmus. 

 It receives the food from the mouth, and the air passes hy the 

 same passage when the nostrils are closed or obstructed. 

 Seven openings lead to or from this cavity, the posterior nos- 

 trils, namely, being two; the Eustachian tubes leading to the 

 ears, two ; the opening to the mouth, one ; the opening of the 

 v gullet, one ; the aperture leading to the lungs through the 

 larynx and windpipe, one ; seven in all. The trachea is the 

 tube leading into the chest, surmounted by the larynx. By 

 this tube the air passes into the lungs, placed in the thorax, 

 and the oesophagus or gullet passes through the chest and 

 enters the abdomen to expand, as it were, into the stomach. 

 By this tube the food and drink pass into that organ. 



61. Whilst the alimentary bolus is passing from the 

 mouth to the pharynx, the apertures of the posterior nostrils 

 are protected by the pendulous palate ; the tubes leading to 

 the ears by a peculiar mechanism, and by their direction ; 

 the opening leading to the larynx and air passage or trachea 

 Is protected by a cartilage of a singularly wonderful mecha- 

 nism, closing the air tube hermetically whilst the food is 

 passing over its upper surface; the gullet is then the only 

 aperture left by which the food can escape from the pharynx, 

 and this leads directly to the stomach. The movements and 

 cou tractions required to effect these actions are numerous, 

 complex, and quite involuntary; when disturbed, the food 

 may penetrate into the larynx and windpipe, causing for an 

 instant terrible distress, and certain death if not speedily 

 relieved. Finally, the gullet being in part muscular, by its 

 contractions the food is readily propelled into the stomach. 

 It is almost needless to say that the gullet is nearly straight, 

 and that the food does not descend into the stomach by its 

 own grarity. 



Stomachal Digestion or Chy unification. 



62. The food is changed in the stomach into the sub- 

 stance called Chyme. The stomach (Fig. 32), is a mem- 

 branous bag placed transversely in the upper part of the 

 abdominal cavity, and almost immediataly below the dia- 

 phragm ; in man it has the shape of a bagpipe, and indeed it 

 is with the stomachs of animals having this shape that the 



D2 



