DR. PROUT ON ANIMAL CHEMISTRY. 493 
composition. The following is a short account of some of the 
more important varieties of this principle :— 
Gelatine and Albumen .—When almost any portion of an ani¬ 
mal body, except the oleaginous matters, is boiled in water, it is 
separated into two portions, one soluble in water, and forming 
with it a tremulous jelly, or gelatine ; the other remaining inso¬ 
luble, or albumen . These principles exist in very different pro¬ 
portions in different textures, some of them, as the skin, being 
almost entirely convertible into gelatine, while others yield com¬ 
paratively little of it, and consist principally of albumen. Gela¬ 
tine does not exist in a fluid state in any animal compound, and 
has been supposed to be a product of boiling; but this is doubt¬ 
ful. One of its most remarkable properties is that of being con¬ 
vertible, by the action of sulphuric acid, into a species of sugar. 
This is comparatively a recent discovery; but I thought the cir¬ 
cumstance so probable, that I attempted the experiment many 
years ago, when the action of sulphuric acid upon starch was first 
observed, but, on account of an accidental circumstance, did not 
at that time succeed. Gelatine may be considered as the lowest 
kind of albuminous matter existing in animal bodies, and, as it 
were, of an intermediate nature between the saccharine principle 
of plants and albumen; indeed, it may be considered as a sort of 
animal saccharine principle. 
Albumen exists in the fluid state in the blood, and in small 
quantity in certain animal secretions, but it is usually found in 
by far the greater proportion as a solid, or, as it is termed, coagu¬ 
lated albumen. Fibrin, another modification of the albuminous 
principle, occurs in the blood in a fluid or at least suspended 
state, but in its most usual state it exists as a tough fibrous mass, 
in which form it constitutes, in conjunction with albumen, the 
basis of the muscular or fleshy parts of animals. It may be also 
obtained from blood by an easy and well-known process. Neither 
albumen or fibrin are capable of being converted into saccharine 
matter by the action of sulphuric acid. 
The substance called gluten , occurring chiefly in the vegetable 
kingdom, and particularly in wheat flour, is a modification of the 
albuminous principle; and according to Berzelius, when sub¬ 
mitted to the action of alcohol, is capable of being separated into 
two principles analogous to the gelatine and albumen of animals. 
These three principles—gelatine, albumen, and fibrin—I am 
disposed to consider as related to one another in the same way 
that we supposed the different varieties of the saccharine principle 
to be related, namely, as all of them having the same essential 
composition, modified by different proportions of water. 
