119 [ern 
a soothing and healing nature, twenty-four hours 
after the blister is first dressed, will usually bring 
about its cessation: and if of a nature approaching 
-to that of the agent first used to vesicate, as fly- 
ointment or savin-ointment, the puriform discharge 
is established, and continues to be thiown off in 
sufficient quantity to reduce somewhat, the general 
tone of the system. In this case the blister be- 
comes an artificial external drain on the body, and 
is termed a perpetual blister ; and it now ceases to 
be a stimulant. In this state a blister is analogous 
in its effects, to setons and issues, which are the 
proper artificial drains, chiefly differing by 
their insertion into teguments and muscles, and 
by their draining from a more circumscribed ex- 
tent. Here then are two opposite consequences of 
a blister—consequences generally within our con- 
trol, and rendering the remedy of two-fold use. 
It fortunately happens, that where the drain of a 
perpetual or (to disuse the improper term for one 
more appropriate) a continued blister, is conceived 
useful or efficacious, the first stimulating impulse 
of the application can do no harm. And in cases 
where the first impulse alone is required, we pos- 
sess the means of checking its commutation into 
the drain, by a course already pointed out. In 
this view of epispastics it must be clear to you, that 
they are important agents in medical and surgical 
_ practice. They have immemorially been much. 
used, from ancient experience of their eflicacy in 
humerous diseases and disorders of the visceral 
system, and for many focal affections of the mus- 
cular and articular frame. In certain fevers of 
low type however, the wasted sensibility of the 
cutaneous system, renders it untangible by their 
power, great and certain as that power is, under 
_ common circumstances of morbid actien. And it 
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