The differences between vegetable and animal bodies appear to depend upon animal matter containing _nitrogen_ in much greater abundance than it is found in vegetables; and hence the decomposition of animal matter by destructive distillation is characterized by the presence of _ammonia_, which is formed by the union of the hydrogen with the nitrogen; and it is sometimes so abundantly generated as to be the leading product: thus when _horns_, _hoofs_, or _bones_ are distilled by themselves, a quantity of solid carbonate of ammonia and of the same substance combined with a fœtid oil, and dissolved in water, are obtained. Hence the preparations called _salt_ and _spirit of hartshorn_ and _animal oil_. The principal animal fluids are _blood_, _milk_, and _bile_. The blood, soon after it is taken from the living animal, separates into two parts, one called the _crassamentum_, which is _red_, and the other _serum_, which is a fluid, and of a pale straw-colour; the crassamentum is a more firm and consistent mass than the serum, by which it is usually, when cool, surrounded. _Milk_ consists of _serum_ or _whey_, _butter_, which while floating on the milk is called _cream_, and _curd_ or _cheese_, which has the leading properties of coagulated albumen. The _bile_, as has been before stated, is a saponaceous fluid consisting chiefly of _albumen_, _soda_, a _bitter resin_, _water_, and some other saline matter. _Fat_, in the dead animal, is merely animal oil in a concrete or hardened state. The principal animal solids besides _bone_, are _albumen_, _gelatine_, and _fibrin_. These substances, in certain states of concretion and combination, form all the solids of animals, and are separable from each other by easy analysis. By whatever means we deprive animal substances of their nitrogen, we reduce them to a state similar to that of vegetables. The muscular fibre, or _flesh_ as it is usually called, when excluded from the air, but particularly if in contact with water, parts with its nitrogen, and is converted into a substance resembling spermaceti, which in its analysis agrees with vegetable expressed oil.