ACTION OF ALKALIES ON THE NERVOUS SYSTEM. 173 



genized vegetable principles, such as quinine, or the 

 alkaloids of opium, &c., which manifests itself, not in 

 the processes of secretion, but in phenomena of an- 

 other kind, physiologists and pathologists entertain no 

 doubt, that it is exerted chiefly on the brain and nerves. 

 This action is commonly said to be dynamic, that 

 is, it accelerates, or retards, or alters in some way the 

 phenomena of motion in animal life. If we reflect, 

 that this action is exerted by substances which are 

 material, tangible, and ponderable ; that they disappear 

 in the organism ; that a double dose acts more power- 

 fully than a single one ; that, after a time, a fresh dose 

 must be given, if we wish to produce the action a 

 second time ; all these considerations, viewed chemi- 

 cally, permit only one form of explanation ; the sup- 

 position, namely, that these compounds, by means of 

 their elements, take a share in the formation of new, 

 or the transformation of existing brain and nervous 

 matter. 



However strange the idea may, at first sight, appear, 

 that the alkaloids of opium or of cinchona bark, the 

 elements of codeine, morphia, quinine, &c., may be 

 converted into constituents of brain and nervous matter, 

 into organs of vital energy, from which the organic mo- 

 tions of the body derive their origin ; that these sub- 

 stances form a constituent of that matter, by the re- 

 moval of which the seat of intellectual life, of sensation, 

 and of consciousness, is annihilated : it is, nevertheless, 

 certain, that all these forms of power and activity are 

 most closely dependent, not only on the existence, but 



