Atropia is a nitrile base, obtained from Atropa Belladonna. All we know of its constitution is, that by the action of strong acids and bases it is decomposed, in accordance with the equation—
So that atropia may be considered as tropia, in which one atom of hydrogen has been replaced by tropyl, the radical of tropic acid.
Atropia has a somewhat complicated physiological action, for it directly influences the functions of the cerebro-spinal and sympathetic nervous systems. The principal effects produced by it on the former system are paralysis of the sensory and motor nerves, and excitation of the spinal cord. By its action on the sympathetic nerves, it influences the contraction of the unstriped muscles; but as the mechanism of this action is by no means exactly defined, we shall merely allude to it in our comparison of the actions of the methyl and ethyl derivatives, with those of the alkaloid itself. In addition to these general actions, atropia influences, in a special manner, the functions of the vagi nerves and of the iris, suspending the cardiac inhibitory power of the former, and producing contraction of the latter.