Acrid.
Bryony.
Elaterium.†
Colocynth.†
Camboge.
Euphorbium.
Hedge Hyssop.
Croton Tiglium.
Ranunculi.
The preceding classification of poisons will not only furnish the practitioner with a general theorem for the administration of antidotes, but it will suggest the different modes and forms of administration of which each particular substance is susceptible; it will shew, that certain poisons may occasion death without coming into contact with any part of the alimentary canal, and that others will produce little or no effect, however extensively they may be applied to an external surface. The first class comprehends such poisons as operate, through the medium of the nerves, upon the organs immediately subservient to life; in the application of such agents it is obvious that they cannot require to be introduced into the stomach, they may convey their destructive influence by an application to any part duly supplied with nerves, and whose extremities are exposed to their action; although at the same time, it may be observed that, in general, poisons of this kind act most powerfully when internally administered, owing to the extensive sympathetic relations of this central organ over every function of the living body. The second class consists of poisons that are incapable of producing any effect, except through the medium of the circulation; whence we shall be enabled to explain and appreciate the various circumstances which may accelerate or retard their operation. Poisons of this class may be applied externally to abraded parts, or even to surfaces covered with cuticle, provided their absorption be promoted by friction; and it may be here observed, that the function of absorption is not performed with the same force in every tissue; as a general proposition it may be said to be energetic in proportion to the number of lymphatics and veins, although the late experiments of M. Majendie have shewn how greatly it is influenced by the state of the circulation.[[213]] If these poisons be administered internally, they find their way into the circulating current either through the branches of the thoracic duct, or those of the venæ portarum; when, as if by a species of election, each substance very frequently expends its venom upon some one particular system of organs. Many of the substances arranged under this second division, have moreover a local effect upon the structure with which they first come in contact; it is thus with Colocynth, and some other bodies; while on the contrary, several of those poisons which are distinguished for their local action, are subsequently absorbed, and are thus as it were enabled to ensure their work of destruction by a double mode of operation. We shall receive ample evidence of this truth, as we proceed in the history of particular poisons. The third class comprises such agents as inflict their vengeance upon the mucous membrane of the stomach, by actual contact, and destroy, by exciting local inflammation.