220 NATURE AND LIFE. 



ing the pupil of the eye when dropped into that organ, or 

 introduced through the usual passages. An extremely mi- 

 nute quantity of this active principle is enough to produce 

 this phenomenon almost instantly, the importance of which 

 Harley was the first to indicate. The exact knowledge 

 of the effects of atropine, which, moreover, acts upon the 

 whole nervous system, furnishes an explanation of the 

 strange circumstances, among others the remarkable mad- 

 ness, of which ancient authors speak when describing some 

 cases of poisoning by belladonna. 



There exists a substance which exerts over the appara- 

 tus of sight an influence directly opposed to that of atro- 

 pine ; this is the Calabar bean, the properties of which were 

 discovered in 1863 by a skillful physician of Edinburgh, 

 Mr. Fraser. This seed, or rather the alkaloid contained in 

 it, and which was isolated in 1865 by a French chemist, 

 V6e, occasions so powerful a contraction and narrowing 

 of the pupil of the eye, that the orifice almost completely 

 vanishes. This constriction of the pupil reaches its highest 

 point about an hour after the active principle has been ad- 

 ministered, and persists for about three hours, and then 

 slowly disappears. This action upon the muscles govern- 

 ing the movements of the pupil depends on the excitement 

 of a particular nerve. Atropine paralyzes this nerve, thus 

 occasioning dilatation of the pupil. There is thus an op- 

 position between the active principle of the Calabar bean 

 and that of atropine, and experience shows that the effects 



same time, the man who had brought him the poison touched him, and 

 after a little while examined his feet and legs ; then, pressing one of his 

 feet strongly, he asked him if he felt it ; Socrates answered, 'No.' After- 

 ward he again pressed the lower part of his legs, and, thus advancing up- 

 ward, he showed us that the body was growing cold, and becoming rigid. 

 He still continued feeling, and said, ' Whenever it reaches the heart he 

 will die.' Already almost all the parts near the lower abdomen were 

 chilled. Socrates then uttered a few words, then went into a convulsion, 

 and died." PLATO. 



