32 IXTRODUCTION. 



All nutriment of every kind being extracted, and the residue 

 havincT readied the last intestine, the rectum, it is hurried on to be 

 expelled. 



Several diseases to Avhich the intestines of cattle are exposed 

 havinn" reference to, or beinor sealed in, different coats or membranes 

 of these vessels, it will be necessary to speak briefly of them. In 

 the first place, they are all wrapped up in a very thin membrane or 

 bag, yet one that possesses considerable strength, called the perito' 

 neum. It secretes a serous fluid, and thus prevents friction in the 

 natural motion of the bovrels over or among each other ; and, encir- 

 cling them all, it retains each pretty much in its place, and restrains 

 too extensive or dangerous motion. The outer coat of the intestines 

 is composed of a reflection or expansion of this membrane, and is 

 liable to a peculiar inflammation. The second coat is muscular, and 

 is composed of a double layer of fibres, by the action of which the 

 food is conveyed or pressed along the canal, and which is called the 

 peristaltic motion. The inner coat is the mucous one, so called from 

 the jelly-like substance by which it is covered ; called also the villous 

 coat, from its velvet-like construction. It is thickly set with innu- 

 merable glands pouring out this mucus, and it is the seat of inflam- 

 mation in over-purging. 



The Mesentery^ or that membrane by which the intestines are en- 

 folded from beginning to end, and through the folds of which the 

 blood-vessels and nerves that supply the intestines, and the veins, 

 and the lacteals pass, is only a duplicature of the peritoneum. In 

 diflerent parts of the mesentery, various glandular bodies are seen : 

 they are the mesenteric glands, the precise use of which is not known, 

 except that they are connected with the passage of the chyle. The 

 enlargement or obstruction of them is sometimes attended with ,yery 

 serious disease, and even with death. The omentum, or caul, is also 

 a portion of the peritoneum. The use of it has never been satisfacto- 

 rily explained. 



The Liver is a large gland, of a dark-red colour, situated in the 

 belly on the right side, and secreting a bitter fluid named bile, or gall. 

 It receives the blood that returns from all the contents of the belly, 

 and which is ])robably so loaded with carbon that it could not all be 

 discharged by the lungs; the quantity of atmospheric air that can be 

 introduced into the lun-Ts in the act of breathino- not containing^ sufli- 

 cient oxygen for the pur])ose. The blood is, therefore, sent into the 

 liver, where it undergoes a process of purification to a certain extent. 

 This inflammable matter, the carbon, is separated in the form of bile; 

 and when thvit is conveyed into the bowels, in order that it may be 

 expelled, it is rendered exceedingly useful there, either by separating 

 the chyle, or quickening the passage of the food, or both. The yellows 

 in cattle is caused either by too great an increase of bile, or by ob- 

 struction of its passage into the intestines. In the first case the sur- 

 ])lus quantity is taken up l)y the absorbents, and enters into the 

 circulation and tinges the blood yellow ; and in the other case, accu- 



