HYDROCYANIC ACID 197 



anesthesia. The same numbness is produced in the stomach and 

 accounts for its sedative action in nausea. 



Nervous System. The central nervous system is first stimu- 

 lated and then depressed. The stimulation is especially marked in 

 the medulla, so that the respiratory center, vasomotor and vagal 

 centers are stimulated, resulting in an acceleration of the respiration, 

 constriction of the blood vessels and slowing of the heart. The blood 

 pressure rises on account of vasoconstriction in spite of the slowing 

 of the heart, but soon falls on account of vasodilatation. The respir- 

 ations are at first accelerated as stated above, but soon become slowed 

 and shallow, death being due to asphyxia. The heart is depressed 

 by large doses. Poisonous doses paralyze the central nervous system. 



Metabolism. Hydrocyanic acid enters the blood very rapidly 

 and while in the circulation profoundly affects metabolism, so that 

 the tissues lose their power of absorbing oxygen. Contrary to pre- 

 vious belief it does not fix the oxygen more firmly to the hemo- 

 globin, but the bright red color is due to the tissues which do not 

 reduce the oxyhemoglobin (Dixon). 



Absorption. Hydrocyanic acid is absorbed rapidly from the 

 mouth or gastrointestinal tract, and may produce symptoms within 

 a few seconds after its administration. 



Toxicology. Hydrocyanic acid is one of the most rapid and 

 fatal poisons. A large dose may cause death by paralysis of the car- 

 diac and respiratory centers, but death is usually due to asphyxia. 



Immediately after the administration of a fatal dose to dogs, the 

 animals make a few gasping respirations, may cry out, go into con- 

 vulsions and die in 2 or 3 minutes from respiratory paralysis. The 

 heart continues to beat for a short time after the respirations cease. 

 If death is somewhat delayed, the pupils dilate, there is incoordina- 

 tion, a weak pulse and convulsions. The fatal dose of diluted hydro- 

 cyanic acid for dogs is 40 — 60 minims, for horses, 4r — 5 drams 

 (Hoare). 



Autopsy. If an autopsy is performed quickly, the character- 

 istic odor of the acid may be detected. The lesions are not constant. 

 The blood may have a venous appearance if death has not taken 

 place quickly, but if immediately, as after a large dose, may be 

 bright red. 



Treatment. Artificial respirations should be started early. On 

 account of the rapid absorption and action, the choice of antidotes is 

 difiicult.. Central nervous stimulants (atropine, strychnine) should 

 be given hypodermically. Hydrogen peroxide is said to be antidotal 

 and is easily obtained. Sollmann recommends sodium thiosulphate 

 (hyposulphite) 100 mils (3 ounces) of a 3 per cent, solution siib- 

 cutaneously (in man) to form the harmless sulphocyanide, but the 

 action of prussic acid is generally so rapid that treatment is not 

 successftj. , : , 



