MATERIA MEDICA AND THERAPEUTICS. 19 



tion has subsided counter-irritants promote absorption of the 

 exudate by local stimulation and tonic action. 



Use only tr. iodine or other mild agents on dogs for counter- 

 irritants. 



CHOICE OF IRRITANTS— 1. To combat chills, rouse 

 nervous depression or overcome functional disturbances, mustard 

 and other rubefacients are indicated. 



2. For more permanent action, in which nutrition is more 

 seriously impaired, as' in chronic pleurisy or phlebitis, the vesi- 

 cants as cantharides are the appropriate remedies. 



3. Where bone, cartilage or tendon is chronically affected, 

 red iodide of mercury, hot iron or escharotics are indicated. 



Astringents. — Contract living tissues, either by coagulating 

 or precipitating albumen or by contracting muscular fibers, the 

 chief are alum, lime, chalk, salts of heavy metals, acids, and 

 alcohol, tannic acid and substances containing tannin, as oak 

 bark, catechu, etc. 



All caustics in diluted form are astringents. These act hy 

 coagulating albumen, but ergot, digitalis, turpentine and other 

 volatile oils contract by acting on the walls of the nutrient ar- 

 terioles. Astringents are used to diminish and modify excessive 

 and faulty secretion, to combat congestion of cutaneous and mu- 

 cous surfaces and arrest limited superficial inflammation. 



Styptics. — Are astringents, used especially to arrest effusion 

 of blood from injured surfaces or vessels. (Applied locally.) 



Some like matico, tow or lint, mechanically check blood 

 flow from superficial vessels, others like most astringents and 

 caustics, coagulate albumen, thereby plugging the leaking vessels, 

 others like ergot, digitalis, ice, and ether-sprays, contract the 

 vessels and allow of natural coagulation, while lead acetate acts 

 both ways. 



Hemostatics. — Are drugs administered internally to stop 

 bleeding. 



Demulcents. — Used for inflamed parts which they come in 

 contact with, they sooth, soften and ensheath, and act chiefly 

 mechanically and resemble emollients. 



They are mostly bland mucilaginous or oily substances, as 

 gums tragacanth, acacia and mucilage, linseed, starch, treacle, 



M 



