The next animal substance we are to examine is _albumen_; this, although constituting a part of most of the animal compounds, is frequently found insulated in the animal system; the white of egg, for instance, consists almost entirely of albumen; the substance that composes the nerves, the serum, or white part of the blood, and the curds of milk, are little else than albumen variously modified. In its most simple state, albumen appears in the form of a transparent viscous fluid, possessed of no distinct taste or smell; it coagulates at the low temperature of 165 degrees, and, when once solidified, it will never return to its fluid state. Sulphuric acid and alcohol are each of them capable of coagulating albumen in the same manner as heat, as I am going to show you. EMILY. Exactly so. --Pray, Mrs. B., what kind of action is there between albumen and silver? I have sometimes observed, that if the spoon with which I eat an egg happens to be wetted, it becomes tarnished. MRS. B. It is because the white of egg (and, indeed, albumen in general) contains a little sulphur, which, at the temperature of an egg just boiled, will decompose the drop of water that wets the spoon, and produce sulphurated hydrogen gas, which has the property of tarnishing silver. We may now proceed to _fibrine_. This is an insipid and inodorous substance, having somewhat the appearance of fine white threads adhering together; it is the essential constituent of muscles or flesh, in which it is mixed with and softened by gelatine. It is insoluble both in water and alcohol, but sulphuric acid converts it into a substance very analogous to gelatine. These are the essential and general ingredients of animal matter; but there are other substances, which, though not peculiar to the animal system, usually enter into its composition, such as oils, acids, salts, &c. _Animal oil_ is the chief constituent of fat; it is contained in abundance in the cream of milk, whence it is obtained in the form of butter. EMILY. Is animal oil the same in its composition as vegetable oils? MRS. B. Not the same, but very analogous. The chief difference is that animal oil contains nitrogen, a principle which seldom enters into the composition of vegetable oils, and never in so large a proportion. There are a few animal acids, that is to say, acids peculiar to animal matter, from which they are almost exclusively obtained. The animal acids have triple bases of hydrogen, carbon, and nitrogen. Some of them are found native in animal matter; others are produced during its decomposition. Those that we find ready formed are: The _bombic acid_, which is obtained from silk-worms. The _formic acid_, from ants. The _lactic acid_, from the whey of milk. The _sebacic_, from oil or fat. Those produced during the decomposition of animal substances by heat, are the _prussic_ and _zoonic_ acids. This last is produced by the roasting of meat, and gives it a brisk flavour. CAROLINE.