MINEEAL OK INOEGANIC POISONS 35 



animals watered at once died within twenty-four hours, the 

 others died after seven or eight days. This- result is intel- 

 ligible on the supposition that the dip is more easily 

 absorbed after extensive dilution, but the author has 

 observed symptoms speedily caused in cattle very soon 

 after licking dry dip. 



As regards mixtures of bluestone and arsenious oxide, 

 Theiler found that 15 grains of each is a safe mixture. 

 With a dose of 30 grains of each, five of thirty-six sheep 

 had prolapsed stomach, and were slaughtered. For blue- 

 stone and Cooper's dip 15 grains of each is regarded as a 

 safe mixture. Thirty grains of bluestone and 15 grains of 

 Cooper's dip, and 30 grains of each, both proved dangerous 

 mixtures, each killing one out of six sheep within twenty-four 

 hours from gastro-enteritis. 



A very remarkable result was obtained on adding common 

 salt and sulphur to the mixture of bluestone and Cooper's 

 dip. A mixture of equal parts of each of these four 

 substances was made. A dose of 45 grains, containing 

 11^ grains each of bluestone and dip, killed five of sixty- 

 five sheep from gastro-enteritis, and a 60-grain dose, con- 

 taining 15 grains each of bluestone and dip, similarly killed 

 sixteen of eighty-eight animals. It thus appears that the 

 addition of salt and sulphur increases the toxicity of the 

 copper sulphate and arsenical dip. 



In respect to the organic derivatives the researches of 

 Ehrlich have well established the dependence of toxicity on 

 the valency, or degree of oxidation, of the arsenic. It has 

 been long known that arsenic acid is less toxic than arsenious 

 acid, and, according to Ehrlich, the toxicity of a pentavalent 

 arsenic compound depends on its relative ease of reduction 

 in the living cells to the trivalent stage.* It is further clear 

 that the position of the arsenic in the molecule is of great 

 significance ; thus the action of the hydride, AsHj, is totally 

 different from that of the acid, II3ASO3, in which the arsenic 

 is part of the radicle or ion, AsOa. It is thus not surprising 

 that among the numerous compounds where pentavalent 

 * See abstract, Veterina/ry News, 1909, p. 155. 



