X 



DILUTED HYDROCYANIC ACID 323 



is held over a bottle containiDg the acid, it soon becomes 

 anaesthetized. Upon mucous membranes, or raw surfaces, 

 prussic acid is rapidly absorbed and exhibits its usual con- 

 stitutional action. 



Action Internal. — Alimentary Canal. — Hydrocyanic acid 

 exerts a sedative effect upon the mucous membrane of the 

 stomach and upper portion of the digestive tract. It is 

 iibrtorbed into the blood, but we are ignorant of its fate or 

 mode of elimination. 



Blood. — In poisoning, the blood becomes first of a bright 

 arterial hue, and later assumes a dark, venous color. The 

 first condition is due to the fact that the blood does not 

 give up its oxygen for some reason. Brunton suggests that 

 it is because the blood is hurried so rapidly through the 

 dilated peripheral vessels that it does not have time to yield 

 up its oxygen. The dark color of the blood is probably 

 owing to asphyxia and accumulation of carbonic dioxide, 

 following the paralytic action of prussic acid upon the 

 respiratory centre. A substance called cyanoliaemoglobin 

 is formed outside the body by hydrocyanic acid when 

 shaken with blood. The acid appears to deoxydize the 

 normal oxyhsemoglobin, and blood thus treated has no ozon- 

 izing property. Cyanohsemoglobin was thoupjht to account 

 for the action of prussic acid, but it does not exist within 

 the body in the blood of poisoned animals. The red blood 

 corpuscles are altered in shape by the action of prussic acid 

 upon blood withdrawn from the vessels. They generally 

 become rounder, then granular, and finally disintegrate and 

 liquefy. But these changes do not occur in the blood during 

 life. The general action of prussic acid is altogether inde- 

 pendent of any influence upon the blood, since the same 

 toxic effect is produced upon the bloodless, or " salt frog " 

 (vessels containing normal salt solution), as upon the normal 

 batrachian. 



Nervous System and Muscles. — Prussic acid has an essen- 

 tially depressing action upon the nervous system as a whole. 

 The brain, cord and nerves become paralyzed by large doses. 



