OF ANIMAL BODIES. lOr 



contrary to the order in which fermentation acts an4 

 spreads. 



5. It is not the digestion of heat ; for the cold maw of 

 a cod or sturgeon will dissolve the shells of crabs and lob- 

 sters, harder than the sides of the stomach which contains 

 them. 



In a word, animal digestion carries about it the marks of 

 being a power and a process, completely sui generis ; dis- 

 tinct from every other ; at least from every chemical pro- 

 cess with which we are acquainted. And the most wonder- 

 ful thing about it is, its appropriation, its subserviency to 

 the particular economy of each animal. The gastric juice 

 of an owl, falcon, or kite, will not touch grain : no, not 

 even to finish the macerated and half digested pulse, which 

 is left in the crops of the sparrows that the bird devours. 

 In poultry, the trituration of the gizzard, and the gastric 

 juice, conspire in the work of digestion. The gastric juice 

 will not dissolve the grain whilst it is whole. Grains of 

 barley inclosed in tubes or spherules are not affected by it 

 But if the same grain be by any means broken or ground, 

 the gastric juice immediately lays hold of it. Here then is 

 wanted, and here we find, a combination of mechanism and 

 chemistry. For the preparatory grinding, the gizzard lends 

 its mill. And, as all mill work should be strong, its structure 

 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, for- 

 asmuch as this is not the sort of animal substance suited 

 for the reception of glands, or for secretion, the gastric 

 juice, in this family, 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 effect in digesting 

 plants unless they have been previously masticated. It only 

 produces a slight maceration ; nearly such as common wa- 

 ter 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. 



