COMPOSITION OF FOOD. 197 



the power of every possible combination, which must vary ac- 

 cording to the number of the nutritive matters, and their re- 

 lative proportions. 



The animal economy exists in very different states at dif- 

 ferent times. It is almost certain that in all states it demands 

 and consumes more than one of the nutritive articles ; but it 

 is probable that in particular states there is a predominating 

 demand for sugar, in another for starch, and so on. From 

 one or two circumstances, it would appear as if sugar were 

 useful or necessary for making fat, while a large quantity 

 may be pernicious if severe labor forbid the formation of fat. 

 Diabetes may perhaps be explained upon this supposition. 

 Mowburnt hay, which contains a large quantity of sugar, may 

 be eaten with impunity by idle or half-worked horses. It is 

 said to make them fat. But in the coaching-stables it is a 

 destructive poison. The sugar enters the circulation, but the 

 system can not appropriate it, and the kidneys have to labor 

 incessantly in order to eject it with the urine, a large quantity 

 of which must be made to carry off the sugar. This is en- 

 tirely a conjectural explanation, the truth or error of which 

 can not be proved without experiments. 



If it were possible to learn what combinations are merely 

 fattening, what invigorating ; what producing bone, what 

 flesh, what milk ; and what the signs which indicate a demand 

 for one substance more than for another, the feeding of horses 

 and other animals would become a science. It is possible 

 that we often err in giving that which is rejected at the time, 

 but which might be highly acceptable in some other state of 

 the system. If we knew, for instance, what combination of 

 gluten, starch, and sugar, were invigorating and what fatten- 

 ing, it would be absurd to give the former to an ox while pre- 

 paring for the butcher, or the latter to a racer while preparing 

 for the course. The ox wants no vigor, and the racer wants 

 no fat. That which is not wanted may be inconvenient, or 

 it may be rejected as useless, the system of the animal not 

 demanding it, or his habits forbidding its appropriation. It 

 will be long, however, ere the feeding of live stock becomes 

 a matter of such accuracy, and perhaps it is not attainable. 

 But it may be good to remeu.ber that what the chymists term 

 nutritive matter, is composed of four substances, which do not 

 each produce the same effect ; that in combination, it is prob- 

 able the effects vary according to the proportions in which 

 the substances operate together ; and that, in particular states 



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