568 GENERAL REVIEW OF THE NUTRITIVE PROCESSES. 



the Animal body is composed, that no great amount of chemical transformation 

 can be required to prepare them for being- appropriated 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 maintenance 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 temperature 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 sub- 

 stances are predominant will serve to sustain the Animal Heat in a cold atmo- 

 sphere. 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 ingested, and the superfluity be thrown upon the Kidneys 

 to eliminate ( 679), disorder of the Urinary Secretion is almost certain, sooner 

 or later, to manifest itself. The quantity of Lithic Acid, in particular, under- 

 goes 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 concre- 

 tions, which are commonly known under the name of " chalk-stones." These 

 deposits usually take place, however, after severe attacks of a peculiar Inflam- 

 mation known as Gout : and this inflammation seems to be dependent upon 

 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 com- 

 pounds 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 rigo- 

 rously enforced, except in early life, or at any rate when the constitution is 

 unbroken by disease or intemperance. Not unfrequently it will be found, 

 that the persistence in a diet of this kind occasions so much disorder of the 

 stomach, as to be quite out of the question. On the other hand, in the " stru- 

 mous diathesis," there would seem to be a low condition of those vital powers, 

 which are concerned in the conversion of the Albuminous materials prepared 

 by the Digestive process, into the Fibrinous matter which is ready for assimi- 

 lation;* so that, by a perversion of the ordinary nutrient actions, Albuminous 



* Some very interesting observations have been recently made on the state of the 

 Blood soon after a meal, by Dr. Buchanan. These are confirmatory of the belief gene- 

 rally entertained, that the milky appearance sometimes presented by the Serum ( 580) 

 is due to the admixture of Chyle. He found that, when a full meal was taken after a 

 long fast, and a small quantity of blood was drawn previously to the meal and at inter- 

 vals subsequently, the Serum, which was quite limpid in the blood first drawn, showed 

 an incipient turbidity about half an hour afterwards; and that its turbidity increased for 

 about six hours subsequently; after which it usually began to clear. The period at 

 which the discoloration is greatest, however, and the length of time during which it con- 

 tinues, vary according to the digestibility of the food. The crassamentum also frequently 

 exhibited a pellucid fibrinous crust; sometimes interspersed with white dots. These 

 experiments indicate, therefore, that the process of assimilation has been but imperfectly 

 performed, when the new materials of blood are introduced into the circulating system; 

 but that, in the state of health, the first stage of this assimilation is usually completed (as 

 shown by the returning transparency of the Serum) a few hours after the ingestion of the 

 food. The persistence of this milky appearance, however, when there is impaired appe- 



