THE ALIMENTARY CANAL. 



89 



hence it is sometimes called the water -bag. Here the 

 food is made into little balls, and returned to the mouth 

 to undergo a thorough mastication. When finally swal- 

 lowed, it is directed, by a groove from the oesophagus, to 

 the third, and smallest, cavity, the manyplies {psalierium), 

 named from its numerous folds, which form a strainer to 

 keep back any undivided food; and thence it passes into 

 the true stomach {ahomasus), from which, in the calf, the 

 rennet is procured for curdling milk in the manufacture 

 of cheese. This fourth cavity 

 is like the human stomach in 

 form and function, and is the 

 only part which secretes gastric 

 juice. The rumen and reticu- 

 lum are rather dilatations of tlie 

 oesophagus than parts of the 

 stomach itself; while the latter 

 is divided by constriction into 

 two chambers, the psalterium 

 and abomasus, as in many other 

 animals. 



In structure, the stomach re- 

 sembles the oesophagus. Tlie 

 smooth outside coat (perito- 

 neum) is a reflection of the 

 membrane which lines the whole 

 abdomen. The middle, or mus- 

 cular, coat consists of three lay- 

 ers of fibres, running length- 

 wise, around and obliquely. The successive contraction and 

 relaxing of these fibres produce the worm-like motion of 

 the stomach, called peristaltic. The innermost, or mucous, 

 membrane, is soft, velvety, of a reddish-gray color in Man, 

 and filled with multitudes of glands, which secrete the 

 gastric juice. The human stomach, when distended, wiU 



Fig. 57. — Vertical Section of the 

 Coats of tlie Stomach : 1, surfaue 

 of mucons membraue, and moiitbM 

 of gastric folliclea ; 2, gastric tubn- 

 li, or follicles ; 3, dense connective 

 tissue ; 4, sabmucons tissne ; 5, 

 transverse muscnlar fibre ; 6, lontri- 

 tudiual muscular fibre ; 7, fibrous, 

 or serous, coat. 



