ANIMAL CHEMISTRY. 



animal could not possibly remain un- 

 changed. 



But, in the young of the carnivora, the 

 weight does not remain unchanged ; on the 

 contrary, it increases from day to day by an 

 appreciable quantity. 



This fact presupposes, that the assimila- 

 tive process in the young animal is more 

 energetic, more intense, than the process of 

 transformation in the existing tissues. If 

 both processes were equally active, the 

 weight of the body could not increase; and 

 were the waste by transformation greater, 

 the weight of the body would decrease. 



Now, the circulation in the young animal 

 is not weaker, but, on the contrary, more 

 rapid ; the respirations are more frequent ; 

 and, for equal bulks, the consumption of 

 oxygen must be greater rather than smaller 

 in the young than in the adult animal. But, 

 since the metamorphosis of organized parts 

 goes on more slowly, there would ensue a 

 deficiency of those substances, the carbon 

 and hydrogen of which are adapted for com- 

 bination with oxygen ; because, in the car- 

 nivora it is the new compounds, produced 

 by the metamorphosis of organized parts, 

 which nature has destined to furnish the ne- 

 cessary resistance to the action of the oxy- 

 gen, and to produce animal heat. What is 

 wanting for these purposes an infinite wis- 

 dom has supplied to the young animal in its 

 natural food. 



The carbon and hydrogen of butter, and 

 the carbon of the sugar of milk, no part of 

 either of which can yield blood, fibrine, or 

 albumen, are destined for the support of the 

 respiratory process, at an age when a greater 

 resistance is opposed to the metamorphosis 

 of existing organisms; or, in other words, 

 to the production of compounds, which in 

 the adult state are produced in quantity 

 amply sufficient for the purpose of respira- 

 tion. 



The young animal receives the constitu- 

 ents of its blood in the caseine of the milk. 

 A metamorphosis of existing organs goes on, 

 for bile and urine are secreted ; the matter 

 of the metamorphosed parts is given off in 

 the form of urine, of carbonic acid, and of 

 water; but the butter and sugar of milk also 

 disappear; they cannot be detected in the 

 faeces. 



The butter and sugar of milk are given 

 out in the form of carbonic acid and water, 

 and their conversion into oxidized products 

 furnishes the clearest proof that far more 

 oxygen is absorbed than is required to con- 

 vert the carbon and hydrogen of the meta- 

 morphosed tissues into carbonic acid and 

 water. 



The change and metamorphosis of organ- 

 ized tissues going on in the vital process in 

 the young animal, consequently yield, in a 

 given time, much less carbon and hydrogen 

 in the form adapted for the respiratory pro- 

 cess than corresponds to the oxygen taken up 

 in the lungs. The substance of its organized 

 parts would undergo a more rapid consump- 



tion, and would necessarily yield to the 

 action of the oxyge'n, were not the deficiency 

 of carbon and hydrogen supplied from 

 another source. 



The continued increase of mass, or 

 growth, and the free and unimpeded de- 

 velopement of the organs of the young 

 animal, are dependent on the presence of 

 foreign substances, which, in the nutritive 

 process, have no other function than to pro- 

 tect the newly-formed organs from the action 

 of the oxygen. It is the elements of these 

 substances which unite with the oxygen ; 

 the organs themselves could not do so with- 

 out being consumed ; that is, growth, or 

 increase of mass in the body, the consump- 

 tion of oxygen remaining the same, would 

 be utterly impossible. 



The preceding considerations leave no 

 doubt as to the purpose for which Nature 

 has added to the food of the young of car- 

 nivorous mammalia substances devoid of 

 nitrogen, which their organism cannot em- 

 ploy for nutrition, strictly so. called, that is, 

 for the production of blood ; substances 

 which may be entirely dispensed with in 

 their nourishment in the adult state. In the 

 young of carnivorous birds, the want of all 

 motion is an obvious cause of diminished 

 waste in the organized parts ; hence, milk is 

 not provided for them. 



The nutritive process in the carnivora 

 thus presents itself in two distinct forms; 

 one of which we again meet with in the 

 graminivora. 



XIII. In the class of graminivorous ani 

 mals, we observe, that during their whole 

 life, their existence depends on the supply 

 of substances having a composition identical 

 with that of sugar of milk, or closely re- 

 sembling it. Every thing that they consume 

 as food contains a certain quantity of starch, 

 or gum, or sugar, mixed with other matters. 



The most abundant and widely-extended 

 of the substances of this class is amylon or 

 starch ; it occurs in roots, seeds, and stalks, 

 and even in wood, deposited in the form oJ 

 roundish or oval globules, which differ from 

 each other in size alone, being identical in 

 chemical composition. (11.) In the same 

 plant, in the pea, for example, we find 

 starch, the globules of which differ in size. 

 Those in the expressed juice of the stalks 

 have a diameter of from ^fo- to T o of an 

 inch, while those in the seeds are three or 

 four times larger. The globules in arrow- 

 root and in potato starch are distinguished 

 by their large size ; those of rice and of 

 wheat are remarkably small. 



It is well known that starch may be con- 

 verted into sugar by very different means. 

 This change occurs in the process of germi- 

 nation, as in malting, and it is easily accom- 

 plished by the action of acids. The meta- 

 morphosis of starch into sugar depends 

 simply, as is proved by analysis, on the ad- 

 dition of the elements of water. (12.) All 

 the carbon of the starch is fo'ind in the 

 sugar- none of its elements have been 



