BRAIN, in anatomy, that soft white mass inclosed in the cranium or skull, in which all the organs of sense terminate, and in which the soul was formerly sup posed principally to reside. See ANA. TONT.
The brain and nerves are the instru ments of sensation, and even of motion ; for an animal loses the power of moving a part the instant that the nerves which enter it are cut. The brain and nerves have a strong resemblance to each other; and it is probable that they agree also in their composition. But hitherto no at tempt has been made to analyse the nerves. The brain consists of two sub stances, which differ from each other somewhat in colour, but which, in other respects, seem to be of the same nature. The outermost matter, having some small resemblance in colour to wood-ashes, has been called the cineritious part ; the in nermost has been called the medullary part Brain has a soft feel, not unlike that of soap ; its texture appears to be very close ; its specific gravity is greater than that of water. When brain is kept in close vessels, so that the external air is excluded, it remains for a long time un altered. Fourcroy filled a glass vessel almost completely with pieces of brain, and attached it to a pneumatic apparatus; a few bubbles of carbonic acid gas ap peared at first, but it remained above a year without undergoing any farther change. This is very far from being the
case with brain exposed to the atmo sphere. Ina few days (at the temperature of 60°) it exhalesh most detestable odour, becomes acid, assumes a green colour, and very soon a great quantity of ammo nia makes its appearance in it. Experi ments show, that, exclusive of the small proportion of saline ingredients, brain is composed of a peculiar matter, differing in many particulars from all other animal substances, but having a considerable re semblance in many of its properties to albumen. Brain has been compared to a soap ; but it is plain that the resemblance is very faint, as scarcely any oily matter could be extricated from brain by Four croy, though he attempted it by all the contrivances which the present state of chemistry suggested ; and the alkaline portion of it is a great deal too small to merit any attention.