S3 
ON CANTHARIS VESICATORIA. 
sure, upon the porous matterupon which the cerate is spread, 
viz.: sheep-skin, chamois-skin, muslin, linen, &c. The ex- 
perience of others, as well as of myself, has taught me that 
the best method is to spread the cerate upon adhesive plas- 
ter cloth, oiled silk, and sheet gum elastic ; but this last 
mode is rather too expensive. The former is attended with 
much less expense than sheep-skin, and prevents the ab- 
sorption of the cantharidin, which is dissolved in the oil, 
and which, of course, is necessary to produce the desired 
result. 
It is sometimes the practice, after spreading the blister, 
to spread upon its surface a small quantity of powdered 
cantharides, to insure the certainty of vesication ; but this is 
unnecessary, especially if proper care has been used in 
preparing the cerate, and the flies used are of the first 
quality. It should be particularly impressed upon the mind 
of the apothecary, that he cannot exert too much scrutiny 
in the selection and in the manufacture of the various pre- 
parations of cantharides, as upon these often wholly de- 
pends not only the continuance of the life of a fellow being, 
but the reputation of both himself and of the physician. 
