AND THE LIVING PRINCIPLE. 



265 



like iron, sulphur, and other extraneous substances 

 in plants ; whilst the want of this ingredient in ve- 

 getables, will be made up by a supply from the at- 

 mosphere, and other sources, to such carnivorous ani- 

 mals as require it. It agrees with all the analogy of 

 Nature, however, that it should require frequentrepe- 

 tition to effectuate this change. And a satisfactory 

 reason why it should do so, is suggested by the very 

 nature of the thing. All the organs and secretions by 

 which the food is digested, are compounded of ma- 

 terials proportioned to the nature of the accustomed 

 food. A change in the proportions of the food, 

 must, therefore, gradually change the proportions 

 of the organs and juices. There can be no doubt 

 but it does so. By the selection of the food, the 

 grazier can, to a very considerable degree, lay on 

 fat or flesh on his stock as he pleases. Now, the 

 food he gives them, differs only in the proportions 

 of the ingredients ; but these differences are suffi- 

 ciently influential to determine the particular sub- 

 stance which is to be formed. It is to be remem- 

 bered, that it is the feeder of the cattle who makes 

 the choice ; and therefore we must conclude, that 

 the digestive operation is a necessary one, like me- 

 chanical attraction, or chemical affinity ; and that, 

 though it may be produced by neither of these, 

 there is no occasion to look for its immediate cause 

 beyond the agency of a law of matter. 



Neither is it more unaccountable, that the bile 

 should mix only with one part of the food which 



