188 CHAL'TEIt 10. 



not required, and is often employed to promote the absorption of abnor- 

 mal deposit. 



The formula for its preparation is : 



Perehloride of Mercury 1 drachm. Rectified spirits 1 ounce. 



Dissolve the Mercury in the spirits, and apply a moderate quantity 

 with a stiff brush. 



385. Action of Vesicants. 



Under the head of Vesicants, otherwise termed Blisters, are included 

 all the applications to the skin, which produce vesicae or watery effusions 

 from the cutaneous blood-vessels. 



Vesicants act much more severe than stimulants, and produce a deeper 

 seated inflammatory action of the true skin. The quantity and rapidity 

 of the watery effusion vary with particular agent employed. 



The Vesicants in most common use are Cantharides and Biniodide of 

 Mercury. 



Setons and Firing, though they cannot be exactly classed as Vesi- 

 cants, have a similar action, and may properly be conveniently consi- 

 dered in the Chapter on Irritants (No. 19). 



386. Cantharides. 



The Vesicant in most use is Cantharides or Spanish Fly. It" is in 

 general safe and effective, and with proper care does not leave any per- 

 manent blemish. The irritation which it produces is abiding, and hence 

 it is much used in cases of injury to parts of low vital or reparative 

 power, such as tendons and ligaments. It has the advantage that if its 

 effects fail before the process of repair is completed it can be repeated. 



On the other hand it is open to the objection that, when applied over 

 a large surface, or with too great frequency, or to parts in a weak or 

 inflamed state, ib is apt to be absorbed into the system. When so taken 

 up it generally acts on the kidneys and produces great prostration of 

 strength. 



Its effects, however, if becoming too severe, may be diminished by 

 dressing the part with liniment of lead; or the blister may be washed 

 off, and the part dressed with oil. 



Before the blistering liquid or ointment is applied, the hair of the part 

 should be closely clipped or shaved, and the skin washed to remove 

 grease or scurf. 



To prevent the horse from gnawing the blistered part, his head should 

 be tied up for 2 or 3 days, after which a cradle should be put on and the 

 head may be let down. 



A blister of Cantharides may be made as under : 



Cantharides . . 1 part. ' Olive Oil . . 6 or 8 parts. 



To be digested in a water bath and strained through muslin, 

 or Cantharides . 1 part. Lard . . .6 parts. 



Great care should be taken in the purchase of Cantharides, as that 

 sold in inferior shops is frequently adulterated. The Flies should be 

 freshly powdered, and kept in a dark place or in a blue bottle. 



