CAUSTICS. 
453 
grammes of nitrate of silver, when it is wished to produce in 
the bladder, by means of injection, the modifying action of 
this salt. 
It is highly necessary to watch, by means of analyses of 
the urine, the consecutive effects of arsenical caustics. 
Acid nitrate of mercury has many advantages, in conse- 
quence of the double energies of its constituent elements. 
Finally, it is much better to employ chloride of zinc, under 
the form of sparadrap or seton, with regard to the homo- 
geneity, extent, and limitation of the rapid inflammation 
w r hich this caustic causes — conditions which render it the 
most anti-hemorrhagic and safe caustic. 
On the employment of Caustics. 
Various experiments, and especially those tried on fibrine 
and globules united in a clot, and, on the other hand, on the 
muscles, have proved to me how important it is to be very 
careful in managing caustics. 
Clots are small masses with shining surfaces, formed of 
tender and penetrable paste ; the muscles are fibrous tissues, 
more or less closely united, into which corrosive liquids can 
easily sink, and caustics are usually either liquids or very 
deliquescent solids, which are thus in danger of passing 
through the tissues, unless all necessary precautions are 
taken. Chloride of zinc itself, the eschar of which so per- 
fectly retains its form, would infallibly fuse, were it not for 
the precautions of M. Canquoin in the preparation of his 
escharotic paste . 
Numerous substances have consequently been employed 
as excipients ; some are inert, such as asbestos ; others 
slightly and only partially modify the composition of the 
caustics, as yolk of egg, flour, &c. ; and in all cases, the best 
are those which best fulfil the conditions of forming — 
1st. A sufficient soft paste to take the form of the parts. 
2d. A paste of sufficient tenacity to prevent the caustic 
from flowing (those which soften at once flow at last). 
3d. A paste sufficiently charged with corrosive matter to 
cauterize at one application. 
For these purposes the following matters have been em- 
ployed with various success : asbestos, precipitated silica, 
charcoal, tinder, lint, saffron, gum tragacanth, yolk of egg, 
and flour. — Condensed from e The Chemist 
