VESSELS OF ANIMALS. 11^ 



and here we find, a combination of mechanism aiu' chem- 

 istry. For the preparatory grinding, the gizzard lends its 

 mill ; and as all mill- work should be strong, its btructure is 

 so beyond that of any other muscle belonging to the animal. 

 The internal coat also, or lining of the gizzard, is, for the 

 same purpose, hard and cartilaginous. But, forasmuch as 

 this is not the soi't of animal substance suited for the reccp* 

 tion of glands, or for secretion, the gastric juice, in this fam- 

 ily, is not supplied, as in membranous stomachs, by the 

 stomach itself, but by the gullet, in which the feeding- 

 glands are placed, and from which it trickles down into the 

 stomach. 



In sheep, the gastric fluid has no eflect in digesting 

 plants, unless they have been previously masticated. It 

 only produces a slight maceration, nearly such as common 

 water would produce, in a degree of heat somewhat exceed- 

 ing the medium temperature of the atmosphere. But, pro- 

 vided that the plant has been reduced to pieces by chewing, 

 the gastric juice then proceeds with it, first, by softening its 

 substance ; next, by destroying its natural consistency ; and, 

 lastly, by dissolving it so completely as not even to spare the 

 toughest and most stringy parts, such as the nerves of the 

 leaves. 



So far our accurate and indefatigable abbe. Dr. Stevens 

 of Edinburgh, in 1777, found, by experiments tried with 

 perforated balls, that the gastric juice of the sheep and the 

 ox speedily dissolved vegetables, but made no impression 

 upon beef, mutton, and other animal bodies. Mr. Hunter 

 discovered a property of this fluid of a most curious kind 

 namely, that in the stomach of animals which feed upon 

 flesh, irresistibly as this fluid acts upon animal substancefc'. 

 it is only upon the dead substance that it operates at all. 

 The livi7ig fibre suffers no injury from lying in contact with 

 i\. Worms and insects are found alive in the stomachs of 

 such animals. The coats of the human stomach, in a healthy 

 slate, are insensible to its presence ; yet in cases of sudden 



