322 OF DIGESTION AND NUTRITIVE ABSORPTION. 



namely, that Gelatin may be advantageously, mixed with albumen, fibrin, 

 gluten, &c., and those other ingredients which exist in meat-soup and bread; 

 but that, when taken alone, it has little more power of sustaining life than 

 sugar or starch possesses ; and that, even when bread is united with the gela- 

 tin-soup, it does not give it the requisite power of nutrition. 



432. If the non-azotized compounds, which exist so largely in the food of 

 Herbivorous animals, are not destined to form part (in any considerable degree 

 at least) of their tissues, the question arises, what becomes of them ? It is 

 not enough to say that they are deposited as Fat ; since it is only when a 

 large quantity of them is taken in, that there is any increase in the quantity 

 of fat already in the body. We shall hereafter see, that they are used up in 

 the process of Respiration, one great object of which is, to produce a certain 

 amount of heat, sufficient to keep up the temperature of the body, in warm- 

 blooded animals, to a high standard. We might almost say with truth, that a 

 great part of the Oleaginous and Saccharine principles is burned within the 

 body, for this purpose. The process will be hereafter considered more in 

 detail; and at present we need only stop to remark upon the adaptation 

 between the food provided for animals in different climates, and the amount 

 of heat which it is necessary for them to produce. Thus the bears, and seals, 

 and whales, from which the Esquimaux and the Greenlander derive their sup- 

 port, have an enormous quantity of fat in their massive bodies : this fat is as 

 much esteemed as an article of food among these people, as it would be thought 

 repulsive by the inhabitants of southern climates; and by the large quantity 

 of it they consume, they are able to support the bitterness of an Arctic winter, 

 without appearing to suffer more from the extreme cold than do the residents 

 in more temperate climes during their winter. On the other hand, the ante- 

 lopes, deer, and wild cattle, which form a large proportion of the animal food 

 of savage or half-cultivated nations inhabiting temperate or tropical regions, 

 possess very little fat; and the comparatively small supply of carbon and 

 hydrogen, whose combustion is required to keep up the bodily temperature of 

 the inhabitants of those regions, is derived from the flesh of those animals in 

 the manner that will be presently explained. Every one knows how much 

 less vigorous the appetite becomes, during the heat of summer, than it is 

 during the colder portion of the year ; and this is a natural result of the dimin- 

 ished demand for the fuel required to maintain the temperature. And one 

 great means of preserving the health, during a prolonged residence in a hot 

 climate, is to attend to the dictates of Nature, in regard to the quantity of food 

 ingested ; instead of endeavouring (as is the prevalent practice) to stimulate 

 the appetite by artificial provocatives. 



433. It has been already stated ( 83), that all the living tissues of the body 

 are continually undergoing a sort of death and decay ; and they do this the 

 more rapidly, in. proportion as they are called upon for the discharge of their 

 functions ( 646). This is, consequently, the chief source of the constant 

 demand for aliment, capable of replacing that which has been lost. Even in 

 young actively growing animals, the quantity of .aliment required for the 

 increase of their bodies, constitutes but a very small proportion of that which 

 is taken in : of the remainder, a. part is at once rejected as indigestible ; and 

 the rest is appropriated to the repair of the waste which is continually going 

 on. This waste is much greater in young animals than in adults ; for all 

 their vital processes are more actively and energetically performed ; their 

 movements are quicker in proportion to their size ; and injuries are more 

 speedily repaired. Now of this waste, the chief part is carried out of the body 

 by the various processes of excretion; and among these, the Respiration, by 

 which a large quantity of carbon and hydrogen is carried off in the form of 

 carbonic acid and water, is of the most constant importance, on account of the 



