360 MANUAL OF EQUINE MEDICINE. 



Method of Detection of Lead in the Tissues or the Urine. — - 

 The tissues should be dried and incinerated in a porcelain 

 vessel. 



The ash should be heated with a small quantity of strong 

 nitric acid, and then evaporated to dryness. The nitrate of 

 lead thus formed may be dissolved out of the residue by 

 water, and filtered. 



A portion of this liquid, evaporated on a slide, will yield 

 crystals of nitrate of lead, which may be identified by : 



(1.) Covering them with a solution of iodide of potas- 

 sium, when they acquire a brilliant yellow colour. 



(2.) Turning black on the addition of ammonium sul- 

 phide. 



The remainder of the liquid, after filtration, may be 

 treated with a current of sulphuretted hydrogen gas. 



A brown colour or a brown precipitate, not readily dis- 

 solved by nitric acid, indicates the presence of lead. 



The metal itself may be obtained, if necessary, by plung- 

 ing zinc into a portion of the acidulated liquid (Taylor on 

 Poisons). 



Absorption of Lead. — Concerning the absorption of lead, 

 in acute and chronic poisoning by this substance, Dr. Taylor 

 says both in acute and chronic cases the metal, in some 

 form, is found more or less in all the soft organs of the 

 body. 



The blue line on the gums affords an instance of its de- 

 position in these parts, the colour being probably due to the 

 conversion of the deposited lead into sulphide. 



Lead was found by Tiedemann in the blood of poisoned 

 animals ; and Professor Cozzi found it in the blood of a 

 person labouring under lead colic. 



The urine appears to be the great channel of elimination ; 

 and Taylor found traces of it in the milk of a cow poisoned 

 by lead paint. 



