Ll8 NATURAL THEOLOGY. 



Of the gastric juice, the immediate agent by which that 

 change which food undergoes in our stomachs is effected, we 

 shall take our account from the numerous careful and varied 

 experiments of the Abbe Spallanzani. 



1. It is not a simple diluent, but a real solvent. A 

 quarter of an ounce of beef had scarcely touched the stomach 

 of a crow, when the solution began. 



2. It has not the nature of saliva ; it has not the nature 

 of bile ; but is distinct from both. By experiments out of 

 the body, it appears that neither of these secretions acts upon 

 alimentary substances in the same manner as the gastric 

 juice acts. 



3. Digestion is not 2yi^iref action, for the digesting fluid 

 resists putrefaction most pertinaciously ; nay, not only checks 

 its further progress, but restores putrid substances. 



4. It is not ^ ferjnentative process, for the solution begins 

 at the surface, and proceeds towards the centre, contrary to 

 the order in which fermentation acts and spreads. 



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

 a cod or sturgeon will dissolve the shells of crabs or lobsters, 

 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, distinct 

 ii'om every other, at least from every chemical process with 

 which we are acquainted. And the most wonderful thing 

 about it is its appropriation — its subserviency to the partic- 

 ular 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 while it is whole. Entire grains of barley, en- 

 closed in tubes or spherules, are not affected by it. But ii 

 the same grain be by any means broken cr ground, the gas- 

 tric juice immediately lays hold of it. Here then is wanted. 



