728 PLASTERS 



The siliceous pastes do not impair skin secretion as fatty 

 bodies do, and, moreover, leave a protective powdery coating 

 on the skin. They are hence indicated, in some cases of 

 moist eczema and other irritable conditions of the skin. 



Cerates are stiff ointments containing wax. 



Pomades are preparations of soft consistence with a basis 

 of lard, lanoline, vaseline, or glycerin of starch, in which is 

 incorporated various active agents, anaesthetics, antiseptics, 

 astringents, etc. 



PLASTBRS-EMPLASTRA 



Plasters are adhesive substances, usually containing lead 

 oxide, conjoined with resin, wax, soap, fats, tar, or pitch ; 

 are conveniently kept in rolls ; and are prepared for use by 

 being melted and spread on calico, linen, or leather. The 

 equable pressure of a well-applied plaster gives support and 

 protection ; retards evaporation, and hence raises topical 

 temperature ; increases glandular activity ; and sometimes 

 also hastens removal of inflammatory products. Plasters 

 are rendered more stimulating by addition of mustard or can- 

 tharides ; more soothing or anodyne by addition of opium 

 or belladonna. 



Ordinary plasters are less useful in veterinary than in 

 human practice ; for in the lower animals they are apt to be 

 displaced by movements, the action of the panniculus car- 

 nosus, and by the patient rubbing or gnawing them. Where 

 they are to remain on for several days or weeks, the melted 

 ingredients are applied directly to the skin, and covered first 

 with finely chopped tow or lint, and then with a linen or 

 leather bandage. Plasters of this kind are popularly known 

 as charges, and were formerly much used in some forms 

 of lameness. They are serviceable when properly applied 

 in preventing undue motion of injured parts. For open 

 joint a useful plaster is made by shaking together one Ib. 

 shellac and one pint methylated spirit. The hair around the 

 wound is clipped, a small piece of oiled silk is laid on, 

 and the adhesive solution painted on with a camel's hair 

 brush until a firm shield is formed. Adhesive or supporting 

 plasters may be prepared with starch, silicate of potash, 



