248 
and fixed oils, resins and wax, are more susceptible 
of change than woody fibre when exposed to air 
and water; but much less liable than the other 
vegetable compounds ; and even the most inflam- 
mable substances, by the absorption of oxygene, 
become gradually soluble in water. 
Animal matters in general are more liable to 
decompose than vegetable substances; oxygene is 
absorbed, and carbonic acid and ammonia formed 
in the process of their putrefaction. They produce 
foetid compound elastic fluids, and likewise azote : 
they afford dark-coloured, acid, and oily fluids, and 
leave a residuum of salts and earths mixed with 
carbonaceous matter. 
The principal substances which constitute the 
different parts of animals, or which are found in 
their blood, their secretions, or their excrements, 
are gelatine, fibrine, mucus, fatty, or oily matter, 
albumen, urea, uric acid, and different acid, saline, 
and earthy matters. 
Of these gelatine is the substance which when 
combined with water forms jelly. It is very liable 
to putrefaction. According to M. M. Gay Lussac 
and Thenard, it is composed of 
47.88 of carbon. 
27.207 — oxygene. 
7.914— hydrogene. 
16.998 
These proportions cannot be considered as de- 
finite, for they do not bear to each other the ratios 
of any simple multiples of the number represent- 
ing the elements ; the case seems to be the same 
with other animal compounds : and even in vege- 
