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movements become less frequent and forcible, the animal giving an occa- 

 sional 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 depression of the brain, 

 spinal cord, nerves, muscles, and the three great medullary centres con- 

 trolling the heart, respiration and vessels. It acts as a poison by inter- 

 fering with oxidation processes in the body. Topically applied, hydro- 

 cyanic acid also paralyzes nerves and muscles, and acts therapeutically 

 as a local sedative and anesthetic. 



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 unconsciousness, 

 the pupils become dilated, there are muscular tremblings and clonic or 

 tonic spasms. Defecation and micturition occur, and erections often 

 ensue in the male. Respiration ceases before the cardiac pulsations. 



Three stages may be distinguished in fatal poisoning. First: a very 

 short period elapses before the symptoms appear. There are giddiness, 

 difficult breathing, and slow pulse in this stage. Second: the pupils 

 dilate, vomiting may occur, and the animal utters loud cries. Spasmodic 

 defecation, micturition and erections may be present, with convulsions 

 and unconsciousness. Third: the last stage is characterized by collapse, 

 spasms, general paralysis and death. The subacute form of poisoning 

 may ensue and prove fatal, or, owing to the volatile character of the 

 drug, complete recovery may take place within one-half or three-quar- 

 ters of an hour. Occasionally dogs continue to be paralyzed for several 

 days and get well. The minimum fatal dose recorded in man is x\ 

 of a grain of pure acid, or about 50 drops of the medicinal solution, 

 and the same for dogs. Four to five drams of the diluted acid fre- 

 quently, but not invariably, cause subacute poisoning and death, in 

 horses, within an hour. One to two drams of the pharmacopeial prep- 

 aration usually kill dogs within ten minutes. 



Prussic acid is commonly used to destroy the domestic animals, but 

 the intrathoracic injection of strychnine is often preferable for the de- 

 struction of the smaller animals. Two to four drams of the medicinal 

 acid are to be given to dogs and cats of the ordinary size, and certain, 

 painless, and rapid death will occur if a fresh preparation of the drug 

 can be obtained. The unopened half-ounce vial, kept by druggists, is 

 recommended. Big dogs, horses, and the other larger animals are not 

 killed rapidly, nor sometimes at all, by great quantities of the diluted 

 acid. Hence, shooting is a more humane and preferable mode of deatl 

 for them. In the experience of the writer, one to two drams of prussic 

 acid saturated with potassium cyanide, failed to kill a horse, when 

 injected directly into the jugular vein. The odor of the acid lingers 

 about the animal for a few hours after death; the eyes are fixed and 



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