ACTION AND USES OF MEDICINES. 155 



cautery. These agents are apt to be much abused, being frequently 

 applied in too strong a form or in too great quantities. Inexperienced 

 people in their desire for a decided effect too often forget the delicate 

 nature of the living structures, with which they have to deal, and the 

 pain which such rough treatment gives. 



Equable well applied pressure, though not a caustic, deserves to be 

 mentioned in this place as a valuable agent in repressing unhealthy or 

 excessive granulations. 



Nitrate of silver is the most convenient application for repressing too 

 luxuriant granulations, or for promoting healthy action in a sore. Corro- 

 sive sublimate is frequently used with advantage in quittor to promote 

 healthy action in the sinuses. Red precipitate induces healthy action in 

 a sore. Nitric acid applied by means of a piece of tow at the end of a 

 stick is used in fungus on the sole of the foot. 



307. Astringents. 



Astringents partake, though only in a modified degree, both of the 

 action of caustics and tonics. Like caustics they combine chemically 

 with albuminous and watery matters, whilst like tonics they act on, 

 brace up, and constringe muscular fibre. 



When given internally they are useful in arresting excessive secretions 

 of the mucous membranes and in bracing up relaxed parts. Hence they 

 are often given in cases of diarrhoea. 



When applied externally, they are beneficial in several ways. They 

 suppress excessive secretions, and hence hasten the formation of healthy 

 cicatrices and promote the process of healing generally. They check the 

 formation of unhealthy granulations ; whilst moreover their constringent 

 action renders them serviceable in reducing superficial inflammation, such 

 as that arising from slight contusions, from inflammation of the mucous 

 coat of the eye, &c. 



Internally opium, catechu, sulphate of zinc, acetate of lead, and rice 

 water are administered. In profuse staling iodine has a very marked 

 effect. 



For external cases alum, the acetate of lead and zinc, and sulphates of 

 zinc, iron and copper are used. Ice, cold water, and cold generally, 

 though they have no chemical effect, deserve places among astringents 

 by virtue of their action in bracing up muscular fibre. All caustics, if 

 much diluted, have an astringent action. 



For an astringent powder equal parts of burnt alum and chalk, or of 

 alum and pipeclay answer particularly well. In cases of indolent sores 

 an ounce of sulphate of copper to a pint of water may be used. 



An astringent lotion may be made by dissolving in water as much 

 powdered sulphate of zinc or acetate of lead as it will take up ; or equal 

 parts of the above may be dissolved together. The lotion may be reduced 

 in strength by adding water according to the nature of the wound to 

 which it is to be applied. An ounce of salt dissolved in a pint of water 

 also forms a very useful mild astringent lotion. 



