128 THE HOG. 



formed of that membrane which invests and retains in its proper 

 position every portion of the contents of the belly. The second 

 layer is muscular, and by its action propels the contents of the 

 stomach gradually onward's. The office of the third is to lubricate 

 the innermost coat, and for this purpose, it is supplied with nume- 

 rous glands surrounded by cellular tissue. The fourth or lining 

 coat is soft, villous, and, in a healthy state, always covered with 

 mucus. The food, having been sufficiently converted into chyme 

 by the action of the stomachs, is gradually propelled through the 

 pyloric orifice by 



THE DUODENUM, 



or first intestine, where it is submitted to the influence of two fluids, 

 the one secreted by the pancreas, the other by the liver, and the 

 combined action of which separates the nutritious from the worthless 

 portion, causing the former to assume the appearance of a thick 

 whitish fluid, and the latter that of a yellow pulpy substance. It 

 next passes into 



THE JEJUNUM AND ILEUM, 



where it undergoes still further alteration, and whence a considera- 

 ble portion of it is taken up by the lacteal vessels which open into 

 these two small intestines, and conveyed away to nourish the frame, 

 and become mingled with the blood and supply the waste in it. 

 These intestines are of equal diameter in the pig throughout their 

 whole extent, and the termination of the jejunum and commence- 

 ment of the ileum is by no means distinctly defined ; the latter is, 

 however, longer than the former, and opens into 



THE CCECUM 



with a valvular opening close to the aperture into the colon. The 

 coscum is a kind of bag supplied with numerous secretory glands, 

 which furnish it with a fluid which once more acts upon those por- 

 tions of the digested food which reach it, extracting from them any 

 nutritive portions which may chance still to remain. The matter 

 having reached the base of this intestine, is returned by the muscu- 

 lar action of its coat, and being prevented by the valve from re- 

 entering the ileum, passes into 



THE COLON, 



the largest of the large intestines, some of the convolutions of which 

 equal the stomach in size, while others are as small as the small in- 

 testines. Here the watery parts of the mass are extracted, and tht, 

 residuum or hard faecal portion is retained for awhile, and finally 

 expelled through the rectum. It will be readily imagined that this com- 



