96 VETEEINAEY TOXICOLOGY 



the equivalent quantity of the acid — at any rate, on intra- 

 thoracic injection ; but this difference is probably due to 

 the fact that potassium cyanide solution does not disengage 

 prussic acid vapour, and is therefore less rapidly absorbed 

 by the pulmonary system. By the acid gastric juices 

 hydrocyanic acid is, however, readily liberated from 

 potassium cyanide. 



It must also be remembered that it is the cyanogen acid 

 radicle or ion ON which is poisonous, and therefore the 

 complex cyanides, e.g., potassium ferrocyanide, and the 

 sulphocyanides, e.g., KCNS, are practically harmless. 



Notable also is mercuric cyanide, Hg(CN)2, which is not 

 easily dissociated — i.e., does not readily yield hydrocyanic 

 acid, and is therefore no more toxic than mercuric chloride. 



Toxic Doses. — Kaufmann quotes for the horse 6 grains 

 in the form of the 2 per cent, solution, and 06 grain 

 similarly for the dog. Finlay Dun states similarly that 

 4 to 5 drachms of the 2 per cent, acid (equivalent to 

 6 grains pure acid) may kill a horse in an hour. As 

 regards potassium cyanide, Kaufmann gives the dose for 

 the horse as 60 to 120 grains (equivalent to 25 to 50 grains 

 of pure acid). For the dog he gives 4'5 grains (equivalent 

 to 1'75 of pure acid). The very much larger doses of 

 cyanide as compared with free acid are no doubt needed, 

 because liberation of the acid is necessary when the salts 

 are given. A heifer^ withstood 22*5 grains pure acid in 

 the form of potassium cyanide, but was killed by 30 grains 

 taken by the mouth, and for the rapid destruction of dogs 

 by intrathoracic injection on the average 1^ grain of free 

 acid in the form of Scheele's acid are commonly used. 



As regards doses of cyanogenetic feeds, such as Java 

 beans, assuming 20 grains as the minimum toxic dose for 

 cattle, and an average hydrocyanic acid yield of 9 grains 

 per pound for dangerous Java beans, it will be evident that 

 at least 2 pounds of beans will be required. In the case of 

 linseed an average hydrocyanic yield of 1"75 grains per 

 pound may be expected, and thus at least 11 pounds of 

 cake would be needed to produce poisoning. Even such 



