NUTRITIVE PRINCIPLES OF PLANTS. 263 
above what amylin contains; so that when the composition of 
amylin is expressed by C,, H,) Oo, that of sugar of milk and 
dry grape sugar will be C,, H,) Oj, plus 2 at. aq.; that of cane 
sugar C,, H,) Oj plus 1 at. aq. 
By merely giving up part of their oxygen, such bodies may 
become fat, the only substance which contains no nitrogen in 
the animal organization. 
The question then may be asked, is a certain portion of food 
without nitrogen absolutely necessary to the existence of the 
life of some animals, merely for the sake of forming fat? Wild 
graminivorous animals have no fat, but more muscle than car- 
nivorous; they become fat before the breeding season or before 
hibernation, when they take little or no nourishment. This fat 
must have some use. 
Man and every other animal are exposed at every period of 
their lives to the unceasing and destructive action of the atmo- 
sphere; with every breath he breathes out a part of his body ; 
every moment of his life he produces carbonic acid, the carbon 
of which his food must replace. 
If we observe a man or other animal in sickness, or at any 
‘time when the body is not supplied with nourishment to com- 
pensate for the continual loss, we find him to become lean; the 
fat is the first to disappear; it vanishes through the skin and 
lungs, in the form of carbonic acid and water, as none of it can 
be found in the feces or urine; it resists the action of the atmo- 
sphere on the body, and is a protection to the organs. But the 
action of the atmosphere does not end with the loss of fat ; every 
soluble substance in the body gives up its carbon, until at last 
all resistance ceases, and death and decay begin, when every part 
of the body enters into combination with the oxygen of the 
air. The influence of the atmosphere is the cause of death, in 
most chronic diseases ; from want of carbon to resist its action, 
that of the nerves and brain is used. In a normal state of health 
and nutrition, the carbon of the carbonic acid must have another 
source. In a second paper, I shall endeavour to show, that the 
carbon of such substances as sugar, gum, and starch, is used for 
the purposes of respiration and the production of animal heat ; 
and that the latter is closely connected with the carbon of the 
food. 
