The secretions are not only mechanical, but chemical separations from the blood; for the substances thus formed, though contained in the blood, are not ready combined in that fluid. The secretions are of two kinds, those which form peculiar animal fluids, as bile, tears, saliva, &c.; and those which produce the general materials of the animal system, for the purpose of recruiting and nourishing the several organs of the body; such as albumen, gelatine, and fibrine; the latter may be distinguished by the name of _nutritive secretions_. CAROLINE. I am quite astonished to hear that all the secretions should be derived from the blood. EMILY. I thought that the bile was produced by the liver? MRS. B. So it is; but the liver is nothing more than a very large gland, which secretes the bile from the blood. The last of the animal organs which we have mentioned are the _nerves_; these are the vehicles of sensation, every other part of the body being, of itself, totally insensible. CAROLINE. They must then be spread through every part of the frame, for we are every where susceptible of feeling. EMILY. Excepting the nails and the hair. MRS. B. And those are almost the only parts in which nerves cannot be discovered. The common source of all the nerves is the brain; thence they descend, some of them through different holes of the skull, but the greatest part through the back bone, and extend themselves by innumerable ramifications throughout the whole body. They spread themselves over the muscles, penetrate the glands, wind round the vascular system, and even pierce into the interior of the bones. It is most probably through them that the communication is carried on between the mind and the other parts of the body; but in what manner they are acted on by the mind, and made to re-act on the body, is still a profound secret. Many hypotheses have been formed on this very obscure subject, but they are all equally improbable, and it would be useless for us to waste our time in conjectures on an enquiry, which, in all probability, is beyond the reach of human capacity. CAROLINE. But you have not mentioned those particular nerves that form the senses of hearing, seeing, smelling, and tasting? MRS. B. They are considered as being of the same nature as those which are dispersed over every part of the body, and constitute the general sense of feeling. The different sensations which they produce arise from their peculiar situation and connection with the several organs of taste, smell, and hearing. EMILY. But these senses appear totally different from that of feeling? MRS. B.