CHEMICAL CAUSTICS. 



117 



Chloride of zinc is an energetic caustic, and may advantageously 

 be used b}- mixing one part zinc chloride with one to four parts of 

 flour, water being added to form a paste. 



Nitrate of silver and the sulphates of copper and zinc are perhaps 

 the caustics most generally employed. Nitrate of silver, or lunar 

 caustic, has only a superficial action. The scab is at first white and 

 soft, later becoming dark 

 under the action of light. 

 Sulphate of copper is 

 cheaper than lunar caus- 

 tic, and is sometimes 

 used to destro}- exuberant 

 granulations. The same 

 is true of sulphate of zinc, 

 which is perhaps less fre- 

 quently emploN'ed. 



The longer the caustic 

 remains in contact with 

 the tissues the more ex- 

 tended is its action, as it 

 continues to spread from 

 the fresh scab. Where 

 the action proves insuffi- 

 cient it may be renewed 

 as soon as the scab is 

 shed. For destroying 

 new growths, caustics in 

 the form of pastilles or 

 rods are sometimes used, 

 an incision being made 

 in the growth for their 

 introduction. In other 

 cases solutions are in- 

 jected. These methods, 

 however, are not to be 

 commended because the 

 range of action of the caustic cannot be controlled. Sometimes 

 a portion of the growth is left, necessitating a second operation ; 

 sometimes the action of the caustic extends to healthy tissue with 

 unfortunate results. The caustics, and especially the more active, 

 produce severe and continued pain during their action. 



Fig. 145. — Bud, point, line, and disc firing irons. 



