432 OF NUTRITION. 



derivation of the fatty compounds from the albuminous substances will be 

 given in the next section, and, like that indicating the origin of the fari- 

 naceous and saccharine compounds from them, is chiefly of an indirect 

 nature. In regard to the analogous compound glycogen, it may be observed 

 that the formation of an amyloid substance is the natural function of the 

 liver, and there is some reason for believing that this is an intermediate 

 stage of the decomposition of albumen into fat; the formation of the glyco- 

 gen being accompanied by the simultaneous appearance of highly nitro- 

 genous substances, such as Glycocholic and Taurocholic acids, which have 

 been shown by Liebig to be readily derivable from albumen, the latter con- 

 taining an important element of albumen, namely, Sulphur. In regard to 

 the albuminous, and as the experiments of Bischoff and Voit appear to 

 prove, the gelatinous constituents of our food also, it is probable that by far 

 the largest part is applied directly to the formation of tissue, including 

 under this term the contents of gland-cells, whilst a much smaller portion, if 

 indeed there be any, termed the " Luxus consumption" by the Germans, is 

 decomposed in the blood without forming tissue. In both instances a kind 

 of decomposition or disintegration takes place under the influence of oxygen, 

 by which, on the one hand, such compounds as Fibrin, (Jhondrin, Keratin, 

 Taurin, Glycin, Leucin, Creatin, Creatinin, Guanin, Sarkin, Xanthin, Uric 

 Acid, Urea, etc., are formed, which are, for the most part, discharged by the 

 Urine and Faeces ; and on the other, certain fatty or saccharine substances 

 are generated, by the further combustion of which the animal heat is main- 

 tained, their ultimate products, consisting of Carbonic Acid and Water, 

 being eliminated chiefly by the skin and lungs. 



344. As regards the fatty constituents of the body, a large proportion is 

 doubtless derived from the oleaginous compounds consumed in the food, 

 though it is certain that a part may also proceed from the metamorphosis 

 or disintegration of both hydrocarbonaceous and albuminous compounds. 

 Of the fats ingested a portion after reduction to the fluid state and minute 

 division is directly absorbed, whilst a smaller portion appears to be de- 

 composed by the pancreatic juice into the fatty acids and glycerin before 

 absorption. It has been suggested by v. Gorup-Besanez that the fat directly 

 absorbed would, under the influence of the active oxygen and alkaline car- 

 bonates of the blood, also soon undergo decomposition into the fatty acids 

 and glycerin, which again, by further oxidation, give rise to formic, propiouic, 

 and other acids. It seems reasonable to suppose that the stearates, oleates, 

 and margarates are directly applied to the formation of adipose tissue. 1 But 

 that the adipose tissue of an animal does not proceed exclusively from the 

 fats ingested with the food is conclusively shown by the experiments of Lawes 

 and Gilbert, 2 who found that in fattening pigs for every 100 parts of fat in 

 the food, 400-500 parts of fat were stored up in the body of the animal. The 

 question then arises, does the excess of fat laid down in the body over the fat 

 ingested proceed from the hydrocarbonaceous or from the albuminous con- 

 stituents of the food ? The experiments of Liebig, Gundlach, Huber, Dumas, 

 and Milne-Edwards upon Bees, showing that if these animals be fed upon 

 pure sugar they are yet able to furnish wax for the comb, and the observa- 



1 See Hofmann (Zeits. f. Biologic, Band viii, p. 153). Raclxiejewski (Virchow's 

 Archiv, Hand x, liii) and Subbotin (Centralblatt, 1870, p. (>7f>) are however op- 

 posed to this view, because they found that although when certain fats with well- 

 marked chemical properties, as .spermaceti, were introduced into the alimentary 

 canal of a dog, they underwent absorption, yet they could not be subsequently de- 

 tected in the subcutaneous fat. 



2 Philosoph. Transact., 1859, p. 543. Sec also Pettenkofer and Voit, Zcitschrift f. 

 Biologic, Band ix. 



