40 PHYSIOLOGY AT THE FARM. 



muscular or contractile, and the mucous or villous, as it is 

 sometimes improperly called, which lines the interior of its 

 cavity. As these coats are severally conjoined by a connective 

 substance, a greater number of coats is sometimes described. 

 It is enough, however, to consider the stomach as composed of 

 three essential coats. The muscular coat consists of exterior 

 fibres, which are longitudinal, and interior fibres, and these 

 are circular; and there are, besides, oblique fibres, the most 

 internal of all Of these three sets of fibres, the circular are 

 the most conspicuous and the most important. Towards the 

 pyloric orifice the circular fibres become blended with those of 

 the duodenum, while the valve of the pylorus is formed by a 

 circular production of muscular fibres enveloped within a fold 

 of the internal coat. The cardiac, or upper orifice of the 

 stomach in the horse, is still more carefully guarded than the 

 pylorus ; here the gullet enters the stomach obliquely through 

 its outer coats, and then its muscular fibres arrange themselves 

 into segments of circles interlacing each other, so that by their 

 contraction the orifice is forcibly closed against the regurgita- 

 tion of the contents of the stomach. 



The mucous lining of the stomach in mammals generally is 

 covered with an epithelium ; but in the horse it has long been 

 observed that what was termed a cuticular lining is very con- 

 spicuous in the left portion of the stomach. It covers nearly 

 one-half of the entire cavity of the organ, and, when inspected in 

 the relaxed state of the organ, it is thrown into wrinkles or rugse, 

 which sometimes assume the appearance of a sort of network. 

 This aspect is, however, entirely owing to an inferior degree 

 of elasticity in the cuticular expansion, in consequence of 

 which it does not contract evenly along with the other coats of 

 the stomach. The same appearance, though in a less degree, 

 is seen, under the same circumstances, throughout the right half 

 of the stomach, and it belongs indeed to the stomachs of mam- 



