MINEEAL OE INOEGANIC POISONS 



49 



neighbouring streams, soils, and herbage.* Thus, in a case 

 brought under the author's notice by Dunstan of Liskeard, 

 the water of a stream was proved to contain both lead 

 and arsenic — the latter being adsorbed by suspended iron 

 oxide. 



Lead is retained by the organs for a long time. The 

 blue line on the gums, supposed to be caused by a deposi- 

 tion of lead sulphide, only disappears very slowly after 

 withdrawal of the cause. The liver, kidneys, bones, nervous 

 tissue, and muscle retain lead in the relative order given. 

 According to Ellenberger the percentages of lead found in 

 those organs of a sheep which during four months had 

 received 164 grammes of lead acetate, were — 



Elimination is slowly effected by way of the bile, urine, 

 salivary, mucous, and cutaneous excretions, and is stated 

 to be hastened by the administration of potassium iodide. 



Toxic Dose. — This cannot be regarded as satisfactorily 

 established. Very usually a large excess of lead remains in 

 the alimentary tract, cows frequently eating lead paint 

 refuse by the pound. The dose is also determined by 

 the nature of the preparation given, the general condition, 

 idiosyncracy, and species of the subject. The following 

 provisional figures may be quoted for minimum toxic doses 

 of acetate of lead : 



Ox 



Horse 

 Sheep 



720 grains 

 7,500 „ 

 450 „ 



The relative tolerance displayed by the horse is a remark- 

 able point, and is on a parallel with the comparative rarity 

 of cases among those animals, the usual victims being 

 in order — cattle, pigs, sheep, dogs. Birds are readily 

 susceptible, but cases of poisoning of them by lead are 



rare. 



* See on this point Taylor, ' Poisons,' 1875, p. 438. 



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