THE EXTERIOR OF THE STOMACHS. 293 



tain, hangs from the roof, and floats free in the stomach, and reaches 

 nearl)' down to the floor. On either side of it is a shorter leaf, and 

 beyond tliat a shorter still, until the outer leaf becomes very narrow. 

 Tiien commences another group, with a long leaf in the centre, and 

 others progressively shortening on each side, until the stomach is 

 filled with these leaves, hanging down from every part of it, floating 

 loosely about, and the lower edge of the longest of them reaching 

 into the continuation of the cesophagean canal. 



The cuticular covering of these leaves is peculiarly dense and 

 strong, and thickly studded with little prominences ; so that when 

 the leaf is examined it exhibits a file-like hardness, that would scarcely 

 be thought possible ; and it is evidently capable of acting like a file, 

 or little grindstone. These prominences are larger and harder 

 toward the lower part of the leaf; and, in the central leaves, assume 

 the form and office of little crotchets, or hooks, some of which have 

 the hardness of horn, so that nothing soHd or fibrous can escape 

 them. 



These groups of leaves vary in number in diff'erent animals, and the 

 number of leaves constituting each group vary too. They float 

 thickest, and the canal is smallest, at the entrance into this stomach, 

 where they are most wanted. Toward the fourth stomach the course 

 is left more open. 



As would be expected, from the complicated mechanism of this 

 stomach, it is more abundantly supplied with blood-vessels and with 

 nerves than the second, or even than the first, although that is many 

 times larger than the third. 



f. The abomasum, or fourtlv stomach, is lined by a soft villous mem- 

 brane, like the digestive portion of ordinary stomachs. It also 

 contains a great number of folds, or leaves, somewhat irregularly 

 placed, but running chiefly longitudinally. They are largest and most 

 numerous at the upper and wider part of the stomach ; and one of the 

 folds, in particular, is placed at the entrance into the abomasum, yield- 

 ing to the substances which pass from the third stomach into the fourth, 

 and leaving, as it were, a free and open way, but opposing an almost 

 perfect valvular obstruction to their return. This explains the reason 

 why vomiting is so rare in the ruminant ; and that when it does 

 occur, it must be produced by such violent spasmodic eff"orts as to 

 cause or indicate the approach of death. See g and h. p. 288. 



Toward the lower and narrower part of the stomach these folds 

 are less numerous and of smaller size : they are also more irregular 

 in the course which they take ; some of them running obliquely and 

 even transversely. This coat of the stomach, when the animal is in 

 health, is thickly covered with mucus, while, from innumerable glands, 

 it secretes the gastric juice, or true digestive fluid. 



The pyloric or lower orifice of this stomach is guarded by a rounded 

 projecting thick substance, by which the entrance into the intestine 



