1 86 On the Classification of Poisons, [Sept. 



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 show that certain poisons may occasion death without 

 coming into contact with any part of the alimentary canal, and 

 that others will produce Httle or no effect, however extensively 

 they may be applied to an external surface. The first class com- 

 prehends such poisons as operate, through the medium of the 

 nerves, upon the organs immediately subservient to hfe ; 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 adminis- 

 tered, 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 circum- 

 stances 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 ener- 

 getic in proportion to the number of lymphatics and veins, 

 although the late experiments of M. Majendie have shown how 

 greatly it is influenced by the state of the circulation. 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 vena par tar urn; 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. 



