THERAPEUTICAL EFFECTS OF MEDICI5ES.
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be better, therefore, either to extend the meaning of the term counter-irri-tant, or to employ some other, such as counter-morbific.
The older writers employed two terms, Revulsion and Derivation; thefirst was applied to those cases in which the secondary disease occurredin a part remote from the seat of the primary affection ; the second was,on the contrary, confined to those instances in which the secondary wasproduced in the neighbourhood of the primary disease. For example,leeches or blisters applied to the feet in apoplexy were called revulsives,but the same applications to the head, in the same disease, would bederivatives. There is, however, no real distinction between them, theiroperation being similar; for revulsion was, even in their own sense of theword, only derivation at a distant part.
Topical applications are frequently counter-irritants. Thus we seestimulant washes, applied to the eye, cure ophthalmia ; and they operate,apparently, by altering the morbid action, and substituting a milder andmore easily cured disease for the one previously existing.
Using the term, therefore, in its most extended sense, we see our list ofcounter-irritants is a most extensive one. It comprehends emetics, pur-gatives, diffusible stimulants, mercury, blisters, cauteries, issues, setons,moxa, blood-letting, (including arteriotomy, venesection, cupping, andleeches,) irritating lavements, frictions, sinapisms, rubefacients, the hotand cold baths, and even mental impressions. That is, all these agentsexcite some action in the system which has a relation (oftentimes bene-ficial) with the morbid action: to use Dr. Parry’s words, these agents curedisease by conversion.
The most unsatisfactory part of our subject is, the theory or hypothesisof the manner in which the mutual relations of diseased actions areeffected. Dr. Parry presumes most diseases consist in local determina-tions of blood, and that it is a law of the human constitution that exces-sive morbid determination to two different parts shall not exist in thesame person at the same time. Neither of these assumptions, however, isquite correct; but if both were true, they still leave untouched the ques-tion how determination of blood to one organ is cured by producing adetermination to another. To account for it, some assume that the sys-tem can produce only a certain quantity of nervous energy, and that, asin every disease, there is an undue or preternatural distribution of ner-vous energy, so the production of an artificial disease in one part must,by consuming the nervous energy, diminish the disease in another. Butthe whole hypothesis is grounded on assumptions perfectly gratuitous andincapable of proof. As Dr. Pring justly observes, were this hypothesistrue, it would lead us to employ not bleeding, purgatives, blisters, and allindirect remedies in hepatitis or consumption, but the exercise of thetreadmill for a few hours ; so that a patient labouring under phrenitis orpneumonia should be made to walk fifteen or twenty miles a day, bywhich it would be presumed so much nervous energy woidd be consumedin the aims and legs, that there could not possibly be any preponderanceor excess in any other seat.
Let us, then, discard absurd hypotheses of this kind ; and for the pre-sent be content with the knowledge of the fact that one disease, whetherartificially or spontaneously generated, will often, but not invariably,supersede another.