ON THERAPEUTICS. 
383 
have found effective in acidity of the fluids in the stomach; 
but, in the treatment of chronic derangements which require 
antacids, we have invariably given the salts of potash or 
soda, which are equally active, and free from any objection on 
the score of the insolubility or medicinal effects of the com¬ 
pounds formed by their decomposition in the system. 
Externally antacid solutions are useful in allaying the irri¬ 
tation present in pruritus, or any of the numerous forms of 
surfeit; their influence depending upon the neutralizing of 
any acid secretion, and probably still more upon their power 
of softening the cuticle, and removing any irritating particles 
from the surface. 
CAUSTICS. 
Agents which decompose or destroy the textures to which 
they are applied are termed caustics or escharotics; they act 
principally by removing the fluids from the textures by virtue 
of their affinity for water; the formation of a dry scab or 
eschar consequent^ follows almost immediately upon the 
employment of the caustic, the structure is disorganized, and 
a mass of dead matter left in its place, to be ultimately re¬ 
moved in the course of the suppurative action which succeeds. 
Caustics are divided by Mialhe into cs coagulants” and 
(< solvents.” 
Coagulants are those which form 'with the tissue a solid 
eschar; such are the mineral acids, nitrate of silver, sesqui- 
chloride of antimony, and chloride of zinc, none of which 
undergo absorption, or produce any medicinal effects upon 
the system. Sulphate of copper, bichloride of mercury, 
nitrate of mercury, form at first a solid eschar, which ulti¬ 
mately is dissolved in the fluid of the part, and in this state 
may produce decided effect upon the organism. 
Solvents, such as caustic potash and arsenious acid, 
occasion the formation of soft eschars they are consequently 
readily absorbed; and, in the case of the arsenical prepara¬ 
tions, particularly require great caution in their employment. 
The actual cautery, as the hot iron is termed, differs in its 
action from the potential cautery, as the various caustics are 
called, as it forms no combination with the textures, but 
merely dissipates the fluid portions, and leaves an eschar of 
carbonaceous matter upon the surface. Subsequent to the 
formation of the eschar, inflammation occurs in the sur¬ 
rounding living structures, the dead part is detached and 
thrown off by the suppurative process; granulation and 
cicatrization complete the reparative action, and according to 
