CANTHARIS VESICATORIA. 199 



" The Cantharides in powder is mixed with lard and wax, so as 

 lo form a plaster of a proper consistence which is applied to the 

 part, generally for 10 or 12 hours ; at the end of that time the 

 cuticle is raised, forming a vesicle ; this is then cut, to allow the 

 serous fluid to be discharged, and the inflamed part is dressed with 

 any mild ointment. The principal circumstance which requires 

 caution in the application of the cantharides plaister, is that deter- 

 mination of action to the neck of the bladder which gives rise to 

 strangury. This is more peculiarly liable to occur where the sys- 

 tem is uncommonly irritable, where the blister is large, or where it 

 is applied to a newly abraded surface, as to the head recently shaved; 

 and as it is a very painful affection, not easily removed, care ought 

 to be taken to guard against it. Camphor has been sometimes 

 added to the blistering plaster, with the view of obviating this. 

 But it is doubtful if it has any such effect : the plentiful use of 

 diluents, while the blister is applied, prevents it much more cer- 

 tainly ; and it is always proper when a blister is applied, especially 

 if large, or in inflammatory diseases, to order the patient to drink 

 freely of any mild diluent liquor. Where the strangury does occur 

 from the application of a blister, it is best relieved by an enema of 

 tepid water, with a little expressed oil, and 30 or 40 drops of tinc- 

 ture of opium, and by the use of the warm bath, or warm fomenta- 

 tions. 



" In some diseases, as in apoplexy, it is of importance to be 

 certain of the operation of an epispastic, and to have its effect pro- 

 duced in a short time. To attain these, a compound plaster is 

 ordered by the Edinburgh College — Emplast. Meloes Vesicat. 

 Comp. — in which the stimulating power of the cantharides is in- 

 creased by the addition of other acrid substances, Burgundy pitch, 

 turpentine, verdigris, mustard, and pepper. In the application 

 of this still more caution is necessary to guard against the occur- 

 rence of strangury. 



" After a blister has been raised, it is' often of advantage to con- 

 vert the serous discharge into one of a purulent nature, by exciting 

 suppuration, or to form what is termed an issue : this can easily 

 be effected by the application of any acrid stimulating ointment : 

 one composed of wax and oil, with a small proportion of cantha- 



