GENERAL REVIEW OF THE NUTRITIVE PROCESSES. 671 



CHAPTER XVI. 



GENERAL REVIEW OF THE NUTRITIVE PROCESSES. ANIMAL HEAT. 



1. Review of the Nutritive Processes, with Practical Applications. 



878. THE detailed survey which has been now taken, of the different 

 Functional operations concerned in maintaining the life of the individual, 

 may suggest to us some general views that have important practical applica- 

 tions. In the first place, it has been shown, that the province of the Animal 

 is not to combine Inorganic elements into Organic compounds, fit to be ap- 

 plied to the purposes of Nutrition; but to use those which are prepared for 

 it by the Plant. The nutritive materials thus obtained may be divided into 

 two great classes, the azotized and the non-azotizecL The former have been 

 shown ( 642) to be so nearly identical in composition with the proximate 

 principles of which the Animal body is composed, that no great amount of 

 chemical transformation can be required to prepare them for being appropri- 

 ated by it. The latter are altogether different in character; and whether or 

 not they can, by any process of transformation, be made subservient to the 

 nutrition of the Azotized tissues, it is unquestionable that their ordinary use 

 is to serve as the materials for the Respiratory process, and for the mainte- 

 nance of Animal heat. The demand for these several articles in the system 

 will depend, in regard to the former, upon the amount of Tissue which has 

 been disintegrated and needs repair; and with respect to the latter, upon the 

 amount of Heat which it is necessary to generate, to keep up the tempera- 

 ture of the body to its regular standard. Hence a highly-azotized diet is 

 most required when the greatest amount of muscular exertion is being used; 

 whilst a diet, in which non-azotized substances are predominant, will serve 

 to sustain the Animal Heat in a cold atmosphere. The adjustment of the 

 diet to the wants of the system, is a matter of the greatest importance for 

 the preservation of health. If too great an amount of azotized food be in- 

 gested, and the superfluity be thrown upon the Kidneys to eliminate ( 850), 

 disorder of the Urinary Secretion is almost certain, sooner or later, to mani- 

 fest itself. The quantity of Lithic Acid, in particular, undergoes considerable 

 increase; and, by the removal of its bases through the increased production 

 of other acids, it is very likely to pass out in an insoluble state, giving rise to 

 Gravelly deposits. Or it may accumulate in the Blood, and there combine 

 with Soda; forming a salt which is deposited in various parts (especially in 

 the neighbourhood of the smaller joints), forming concretions, which are com- 

 monly known under the name of "chalk-stones." These deposits usually 

 take place, however, after severe attacks of a peculiar Inflammation, known 

 as Gout; and this inflammation seems to be connected with the accumulation 

 of Lithate of Soda in the Blood. Over this disease a careful regulation of 

 the diet exercises a powerful control. A patient affected with the " Lithic 

 Acid diathesis," may palliate, if not altogether cure his disorder, by rigorously 

 abstaining from the use of any superfluous amount of azotized compounds 

 as food ; and by subsisting as much as possible upon those belonging to the 

 Farinaceous group. It is by no means every case, however, that is capable 

 of alleviation by treatment of this sort ; in fact, it can seldom be rigorously 



