FORMATION OF FAT. 



35 



sequently in that of the heat indispensable 

 for the vital process. 



Experience teaches us that in poultry, 

 the maximum of fat is obtained by tying 

 the feet, and by a medium temperature. 

 These animals in such circumstances may 

 be compared to a plant possessing in the 

 highest degree the power of converting all 

 food into parts of its own structure. The 

 excess of the constituents of blood forms 

 flesh and other organized tissues, while that 

 of starch, sugar, &c., is converted into fat. 

 When animals are fattened on food destitute 

 of nitrogen, only certain parts of their struc- 

 ture increase in size. Thus, in a goose, 

 fattened in the method above alluded to, the 

 liver becomes three or four times larger than 

 in the same animal, when well fed with free 

 motion, while we cannot say that the or- 

 ganized structure of the liver is thereby in- 

 creased. The liver of a goose fed in the 

 ordinary way is firm and elastic; that of the 

 imprisoned animal is soft and spongy. The 

 difference consists in a greater or less ex- 

 pansion of its cells which are rilled with fat. 



In some diseases, the starch, sugar, &,c., 

 of the food obviously do not undergo the 

 changes which enable them to assist in 

 respiration, and consequently to be con- 

 verted into fat. Thus, in diabetes mellitus, 

 the starch is only converted into grape sugar, 

 which is expelled from the body without 

 further change. 



In other diseases, as for example in in- 

 flammation of the liver, we find the blood 

 loaded with fat and oil; and in the composi- 

 tion of the bile there is nothing at all incon- 

 sistent with the supposition that some of its 

 constituents may be transformed into fat. 



XIX. According to what has been laid 

 down in the preceding pages, the substances 

 of which the food of man is composed may 

 be divided into two classes ; into hitrogenized 

 &n([lfion-nitrogenized. The former are ca- 

 pable of conversion into blood; the latter 

 incapable of this transformation. 



Out of those substances which are adapted 

 to the formation of blood are formed all the 

 organized tissues. The other class of sub- 

 stances, in the normal state of health, serve 

 to support the process of respiration. The 

 former may be called the plastic dements of 

 nutrition; the latter, elements of respiration. 

 Among the former we reckon 

 Vegetable fibrine. 

 Vegetable albumen. 

 Vegetable caseine. 

 Animal flesh. 

 Animal blood. 



Among the elements of respiration in our 

 food, are 



Fat. Pectine. 



Starch. Bassorine. 



Gum. Wine. 



Cane Sugai. Beer. 



Grape Sugar. Spirits. 



Sugar of milk. 



XX. The most recent and exact re- 

 searches have established as a universal 



fact, to which nothing yet known is op- 

 posed, that the nitrogenized constituents of 

 vegetable food have a composition identical 

 with that of the constituents of the blood. 



No nitrogenized compound, the compos] 

 tion of which differs from that of fibrine 

 albumen, and caseine, is capable of sup- 

 porting the vital process in animals. 



The animal organism unquestionably pos\ 

 sesses the power of forming, from the con 

 slituents of its blood, the substance of it: 

 membranes and cellular tissue, of the nerve; 

 and brain, of the organic part of cartilages 

 and bones. But the blood must be suppliec 

 to it ready formed in every thing but its 

 form that is, in its chemical composition. 

 If this be not done, a period is rapidly put 

 to the formation of blood, and consequently 

 to life. 



This consideration enables us easily to 

 explain how it happens that the tissues 

 yielding gelatine or chondrine, as, for ex- 

 ample, the gelatine of skin or of bones, are 

 not adapted for the support of the vital pro- 

 cess ; for their composition is different from 

 that of fibrine or albumen. It is obvious 

 that this means nothing more than that those 

 parts of the animal organism which form 

 the blood do not possess the power of effect- 

 ing a transformation in the arrangement of 

 the elements of gelatine, or of those tissues 

 which contain it. The gelatinous tissues, 

 the gelatine of the bones, the membranes, 

 the cells, and the skin, suffer, in the animal 

 body, under the influence of oxygen and 

 moisture, a progressive alteration; a part 

 of these tissues is separated, and must be 

 restored from the blood ; but this alteration 

 and restoration is obviously confined within 

 very narrow limits. 



While, in the body of a starving or sick 

 individual, the fat disappears, and the mus- 

 cular tissue takes once more the form of 

 blood, we find that the tendons and mem- 

 branes retain their natural condition ; the 

 limbs of the dead body retain their connex- 

 ions, which depend on the gelatinous tis- 

 sues. 



On the other hand, we see that the gelatine 

 of bones devoured by a dog entirely disap- 

 pears, while only the bone earth is found in 

 his excrements. The same is true of man, 

 when fed on food rich in gelatine, as, for 

 example, strong soup. The gelatine is not 

 to be found either in the urine or in the 

 faeces, and consequently must have under- 

 gone a change, and must have served some 

 purpose in the animal economy. It is clear, 

 that the gelatine must be expelled from the 

 body in a form different from that in which 

 it was introduced as food. 



When we consider the transformation of 

 the albumen of the blood into a part of an 

 organ composed of fibrine, the identity in 

 composition of the two substances renders 

 the change easily conceivable. Indeed we 

 find the change of a dissolved substance into 

 an insoluble organ of vitality, chemically 

 speaking, natural and easily explained, or 



