An Essay on Fat and Mtiscle. 
247 
globe, of the soils wliicU we cultivate, and of all that live and 
breathe thereon. 
Hydrogen is the next elementary body. It also exists in the 
stale of gas. and is the lightest of all known substances. In com- 
bination with oxvgen, it forms water, being about one-ninth of its 
weight; and it also forms a small per centage of the food of 
animals, which, combining with oxygen in the living organism, 
assists to produce animal heat (8). 
Nitrogen, sometimes called azote, is also known only in the 
form of gas. It exists in the atmosphere to the amount of 79 
per cent, of its bulk : hence it is an essential constituent of the 
air we breathe — serving, as chemists believe, only to dilute the 
oxygen; but it is more probable that it serves some necessary 
purpose in the economy of animals, the exact nature of which has 
not been discovered. All parts of the body of an animal, which 
have a decided shape, contain nitrogen : hence it may be supposed 
to perform certain most important functions, in reference both to 
the growth of plants as well as animals; for the most convincing 
experiments and obsen ations have proved that the animal body is 
incapable of producing an elementary body such as nitrogen out 
of substances which do not contain it ; and it obviously follows 
that all kinds of food fit for the production either of blood, 
cellular tissue, membranes, skin, or muscular fibre, must contain 
a certain amount of nitrogen. 
4. The union of those elements, according to certain laws, in 
various ways, forms v.hat are called the proximate elements of 
nutrition. 
These have been divided, for the sake of distinction, into two 
groups — the azotised and non-azoiised — the former being properly 
designated the elements of mttrition, and the latter the elements of 
fat and respiration. The following analyses of several of these 
bodies will enable the reader to comprehend the nature of this 
distinction : — 
Elements of Null itiou. Elements of Respiration. 
100 parts 
of- 
c 
1 
3 
•5 "3 
"s ^ 
fc 
> 
Vegetable Casein. 
Junes. 
Ox Hlood. 
Blayfair. 
Mutton Fat. 
j CheviL'ul. 
Potato .Starch. 
Uerzelius. 
. 3 
Sugar of Milk. 
Liubig. 
Carbori . . 
54 -2 
59-99 
54-I3S 
54-3) 78-996 
44-350 
42-682 
40-01 
Hydrogen 
7-5 
6-87 
7- Lie 
7-50 II-70U 
6-674 
6-374 
6-73 
Nitrogen . 
13-9 
i5-e6 
15'672 
15-76 1 . . 
Oxygen . 
24-4 
22-48 
23-034 
22-39 9-304 
49-076 
50-944 
53-27 
