ON THE BALANCE OF THE VITAL ECONOMY. 433 



tions of Boussingault, Lehmann, Groner, and Lawes and Gilbert on ducks, 

 geese, pigs, and oxen, showing that on a diet rich in carbohydrates fat is 

 abundantly formed, and either deposited in the tissues or excreted in the 

 milk or fbeces, coupled with the well-known fact that negroes rapidly fatten 

 during the period of cutting the sugarcanes, lead to the conclusion that the 

 fat of the body may be derived from the carbohydrates, and this is supported 

 by the observation of Pasteur, that in the alcoholic fermentation of sugar 

 Glycerin is one of the products. Lawes and Gilbert indeed estimate that 2^ 

 parts of starch must be consumed in the food to produce one part of fat, the 

 proportion of sugar required being somewhat larger. 1 But evidence has also 

 accumulated showing that the fat of the body may be derived from the 

 albuminous compounds; thus Petteukofer and Voit found that on very full 

 or excessive meat diet their dog excreted considerably less carbon than he 

 ingested, though the quantities of nitrogen ingested and egested were almost 

 exactly equal, and as the animal gained in weight and fat was deposited in 

 its tissues, there was strong reason for believing that it was due to the separa- 

 tion of a part of the albuminous compounds in the form of fat. Other facts 

 which may be mentioned as tending to prove the same thing are the produc- 

 tion of adipocere from muscle; the observations of Bloudeau, Hoppe, Kem- 

 merich and Fleischer, that fat can be deposited during a diet composed 

 mainly of cheese, and the formation of fat during the maturing of cheese, 

 and the development of fat in a fasting dog when the animal is slowly poi- 

 soned with phosphorus ; the experiments of Subbotin showing that bitches 

 secrete milk containing the largest amount of fat when the food has been 

 abundant, though composed essentially of lean meat ; the observations of 

 Burdach 2 upon the eggs of Limnteus, showing that in the progress of incuba- 

 tion the fat increases apparently at the expense of the albumen, so that 

 whereas in the early stage the amount of fat is about 7 per 1000 and of 

 albumen about 9.53, in the last stage the amount of fat has increased to 

 about 22 parts, whilst the albumen has fallen to 9.18 in 1000 parts ; and 

 lastly, the recent experiments of Pettenkofer and Voit 3 all afford strong 

 support to the view that the fats may be derived from the albuminous 

 compounds, the observation of these investigators appearing to demonstrate 

 that when a sufficient amount of albuminous food is supplied, fat ingested 

 as such is stored up in the body, the carbohydrates burnt to maintain the 

 animal heat being really derived from the disintegration of the albumen, 

 which they estimate yields about 55 per cent, of its weight of fat. The 

 phenomena presented in nerve-cells and muscular tissue during the patho- 

 logical process of fatty degeneration may also be referred to as supplying 

 additional evidence. The quantity of fat contained in different parts of the 

 body varies considerably, but it is almost universally present. The blood 

 usually contains about 0.4 per cent., .the muscles 3.3, milk 4.3, brain 8, the 

 nerves 22, and adipose tissue 83 per cent. The fatty matters of the Blood, 

 besides being destined to furnish the contents of the Adipose and Nervous 

 vesicles, appear also to be required in the early stages of the production of 

 cells generally. The principal source of their expenditure, however, is that 

 process of combustion by which the heat of the body is maintained ; and the 

 amount deposited in the tissues as fat, may be looked upon as the surplus of 



1 The opponents of the view above given, that f;it may be derived from the Car- 

 bohydrates, contend that the purely chemical evidence is weak, since only fatty 

 acids, poor in carbon, and traces of Glycerin and Glycerides, make their appearance 

 in saccharine fermentations. 



2 F. W. Burdach, De Comment Subst. Prot. in Adipem Dissert., 1853. 



3 Zeits. f. Biologic, Band ix, Heft 1. Weiske und Wildt, Zeits. f. Biologie, Band 

 x, 1874, p. 1. 



