2IO 



ELEMENTS OF PHYSIOLOGY 



long, and lies along the spinal column behind the trachea. 

 It has the three layers found elsewhere in the alimentary 

 canal, and its walls are soft and lie collapsed when no 

 food or drink is passing. The food is under reflex con- 

 trol after passing the fauces. 

 The contraction of the pharynx 

 presses the food down into the 

 esophagus. A ring of the mus- 

 cular tube contracts just above 

 the morsel. This contraction 

 runs down to the stomach, forc- 

 ing the food before it as if a tight 

 ring were slipped down over the 

 esophagus. A contraction of any 

 part of the alimentary canal in 

 this manner, as if a wave were 

 traveling along, is called peri- 

 stalsis. While a horse is drink- 

 ing, the peristaltic waves of the 

 esophagus may be plainly seen 

 along the neck (Plate VII). 



374. The Stomach. The gul- 

 let pierces the diaphragm to the 

 left of the center and enlarges 

 vii). into a pouch called the stomach. 



a, vertebral column; b, esophagus; -j^g or ^ an lj es j us t under the 

 c, trachea; d, larynx; e, epiglottis; J 



/, soft palate and uvula; g, open- diaphragm, mostly on the left 



ing of left Eustachian tube; h, open- ,. J t, ir 



ing of left lachrymal duct; *', hyoid side of the abdomen and hall 

 L, n , baseof skuiii ^A^e covered by the lower ribs. It 



scroll-like, or turbinated bones. J g ca p a ble of holding about tWO 



quarts. When full, it is about a foot long and five inches 

 broad. Its shape is not easily described (Fig. 167). It is 

 placed across the abdomen, and its left end is the larger. 

 Its outline is curved inward above and outward below. 

 When empty, it flattens and its walls touch, and the 



