DILUTED HYDROCYANIC ACID 345 



movements are therefore lessened in frequency throughout 

 the period of its action. Rarely, there is a primary transient 

 stimulation of the centre, so that the breathing is increased 

 in frequency. In the latter stage of poisoning, the breathing 

 is feeble and shallow, and only occurs at long intervals. 

 If death does not supervene immediately from diastolic 

 arrest of the heart, it comes on more slowly by asphyxia. 

 The respiratory movements become less frequent and 

 forcible, the animal giving an occasional gasp, until finally 

 the breathing ceases altogether, while the heart continues to 

 beat for a time. 



Summary. — Prussic acid in any considerable dose exerts 

 a transient stimulation upon the hind-brain, followed by 

 brain, spinal cord, nerves, muscles, and the three great 

 medullary centres controlling the heart, respiration and ves- 

 sels. Topically applied, hydrocyanic acid also paralyzes 

 nerves and muscles, and acts therapeutically as a local 

 sedative and anaesthetic. 



Toxicology. — Prussic acid is one of the most powerful 

 poisons in existence. Death may be instantaneous, or life 

 may be prolonged for over an hour after a lethal dose. 

 More commonly the animal survives for a few minutes, and 

 we observe the following symptoms in dogs : The animal 

 falls, froths at the mouth, the respiration is of a gasping 

 character and occurs at infrequent intervals. There is un- 

 consciousness, the pupils become dilated, there are muscular 

 tremblings, and clonic or tonic spasms. Defsecation and 

 micturition occur, and erections oftan ensue in the male. 

 Kespiration ceases before the cardia<j pulsations. 



Three stages may be distinguished in fatal poisoning. 

 First: a very short period elapses before the symptoms 

 appear. There are giddiness, diffiault breathing, and slow 

 pulse in this stage. Second : the pupils dilate, vomiting 

 may occur, and the animal utters loud cries. Spasmodic 

 defsecation, micturition and erections may be present, with 

 convulsions and unconsciousness. Third : the last stage is 

 characterized by collapse, spasms, general paralysis and 



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