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oesiar actions. Mercuo AOrds an example of this. It en-tera the circulation, and, when accumulated to a Suffciente tent, generalty acts on the saliva gland8- It is on secreting organs that these locat effecis are usualis produced, and frequently the substance is separated with the secreted fiuid, So as to aci ou the secreting vesseis. Such is the casewith the allaesine salis, or xvith nitre, which are secreted by the vesseis of the Edneys, stimulate them at the Same timstio action, and are capille of being detected in the urine by
But the most generat mode in whicli the operation os medicines talaen into the stomach is exteuded, either to the System in generat, or to any particular Oron, is by the medium os nervous communication. Au impression is made onthe fibres of the stomach by the substance received into it, 2nd however dissicula it may be to conceive the mode in Whichthis can be communicated by the nerves to distant paris, thesaci is undo ted, and est lished by the platuest evidelice. Ιt is evident froni the effecis of these substances heing produced in a shorter time aster they have been received into the stomach, than they could he were they to act by belligabsorbed by the chyle into the circulat g in s. The Sti mulus of wine or of Opium received into the stomach wil Iinstantly remove lassitude, and increase the vigo of thoeirculation, or of muscular exertion ; or the Same Si Stan S,
in a larger dose, will, with the fame celerity, depress ali tho functions, and exhaust the po vers of liis. Digitalis givento suffcient extent Will speedij reduco, io a great. degree, the frequency of the pulsu ; or a large doso os cinctiona, gi Venitali an hour besere the expected recurrence of the par XJSinoi au interinittent, ivili prevont iis attach. Ιt has also been proved by experiment, that illis communication os actionis0m the stomach to other puris, in a number os cases, docS
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GENERAL VIEN OF THEuot talae placo where tho brain and spinal marrow have been destr ed, though ille licari aud vascular System have beeii preServed uui ured. 0m thiς susceptibility of impression, aud os communicating action to Other paris, the Stomach becomes an Organos the stast importanco, since, hidependent os iis heing the vehicle by whicli substances are conveyed into the blood, itis that by means of whicli medicines are brought to aci onthe system by the medium of the nerves. It SometimeS happens, hoWever, that a similax extension os action may take place froni other paris ; and heiace effecis may be obta edivom medicines, by applying them to the su face of the body, similar to those whicli they produce When they have been.
received into the stomach. Sometimes the effect is conVeγ-ed by nervolas communic tion, and sonaetimes the substance
applied is absorbed by the lymphatics, and enters the blood.
Opium, applied to the Ain, either in the solid sortii, or in
that of tinctu e, Osten relieves pala, and removes Spasmodicaffections, either general or locul. Tobacco applied to the region of the stomach excites vomiting; and garlic applied tothe feci acts as a powerfui stimulant, and raises the strennii of the pulse. Examples of the second mode of operationare Stilli more frequent. Friction on the sursace is a common method of introducing mercu into the System. By the sanaerucatis oXide os arsenic, tartrate of intimony, and Various other active Substances, may be introducei ; a solution of
Under certa in circumStances, iliis is preserable to their administration by the stomach. Many substances applied to auWOunii, produce important effecis On the system, affectingilie functions of the heuri or brain : in Such cases they applar to act by cnternig the circulation thi ut ille divide luctus of the part to whicli they are applied.
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These are oXamples of the various relations whicli media cines bear to the living system. Me are unable to n8Sim a cause lax these peculiar properites, to aScertain Why the --tion os fonte should be extended to the system in generat, or y that of others should he determined is particular paris, either riviore substances enter the Nood, OP Where they actis the medium os the nerves. But from the possession ossuch properites, it is evident, that their po vers as medicines must be more diversified than is they were merely generat Stimulanis, va ing in the demee of their stimulating po ver ;and sarthor, that distinctions are thus assorded for est lishing a varie of ClaSSeS. Other cause remains to bo potated ovi, by whicli theactions os medicines are divorsised. Besides acting as stimulanis, they somelimes Occasion changes, either mechanicalor chemicat, in the state of the fluids, or of the simple solids, and these changes are productive os medicines effecis. This operation of medicines was formerly supposed to homuoli more extensive than it rosty is. Sufficient weight was not alsowed to tho important sact, that the actions os externat agents ou tho living body are gove ed by latus disserent
froni thoso whicli regulate the actions exerted belween themasses or particles of inanimate mattei'. Honoe wo find in medicat speculations, conStant attemptS to trace the causos of diseases to changes merely mechanical or chemical, to plethora or obstruction, to laxity or rigidity, to tho ab dance of acid or of altati, or to the prefouce of other specisio acrimonios stili tess defined. The cxplanations of the operationsos modicinos wero os courso munded on illese notions, and henco ille distinctions os in spissanis, ait uanis, an tacitis,
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mere mechanical or chemices principies ; und to regurd cxternat powers acting upon it aS producing changes consorm- le to these peculiar properties of lila. Yet stili xve cansomelimeΗ refer a salutary change, effected in the System, orin particular orgatis, to changes mechanical or chemicat intho solids or fluids. Thus; sympionis arising hom irritationmay be removed by lubricating the irritated si tace ; acid intho Stomach may he corrected by the exhibition os eskalses
Sorbent earllis; and urinary concretions may be diεSolv-ed, or at least their increase may be provented, by the eos aikaline remedios. These properties of certain medicineSaro uot pexhaps hi j important; but th demand attention, and they afford sufficient distinctions for the formation
In consorintly to these vieivs, the classification os the articles of tho Materia Medica, Dunded on their medicinal erations, may he est lished. It is only necessa to Ob- Serve, principalty to obviate hasty criticism, that in classis-cutions fouuded on this principio, perfeci precision is not tobe eXpected. The science of medicine is stili in so impersecta State, pRrtiouIarly in What regards the relations os externalagenis to the living system, that both in arranging the classes, and associating the Substances which we place under each. o must frequently regi satisfied with remote analogies, whichwill not est ys bear a strict examination. I his is an impersection ut present unavoidable ; it must either be submit ted io, or such modes of classification inust be altOgether rejected ; and the question therelaro ultimateb is, not whother these arrangements are unobjection tu, but whether the ad-
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UsDER ilio first division os the arrangement I pr0pose, may be placedi those substances whicli exert a generat stimulant operation on the system. of these there axe two subdivisions, the Diffusibie and the Permanent; Ille sermer including the class of N arcotics, with whicli may be associaled, as nos very remote in their operation, the class of Antispas- modios ; the lalter comprising two classes, Tonics and A truagenis. Through these there is a gradual transition homthe moro hi ly diffusibie stimulanis, to those more flow and durabie in thois action. A second division comprehends Locis Stimulanis thogethe action os ivsicli is determined to particulis paris of the system. Such are the classes of Emetios, Calliartios, Emanenagogues, Diuretices, Diaphoretics, Expectoranis, and Sialogogues ; With which may bo associa ted the classes of Errhines, and of Epispastics, launded on direct loces appli
The remaining classes include substances whicli do notoperate according to latus peculiar to the living system. Toone division may be referred those, the effecis of whicli depend on the chemicat changes they produce in the fluids orsoli Is : the clamsos which may be est lishod on this principio ρ Rcfrigeranis, Antacids, Lithontriptios, and pscharotios. To another division belong those, the operation of whicli is purely mechanical,-Diluonis, Demulcenis, Emollienis, and
Under these classes may bo comprehendod est those substances Whicli are capa te os producing salutato changes in the human system, and whicli are used as remedies. A vie vos this classification is exhibited in the folio ing table :
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Frona this arrangement, sciue classes are excluded that have usualty seund a place in others ; but these have eithera eared to me not essentialty different stom those that aro admitted, or to have been Dunded on salse or hypotheticaldistinctionS. There is no great advantage in extending the arrangementinio systematio subdivisions os the classes. The substances under each may solio v each other according to their naturalamities, thela chemicat relations, or analogies in medicinalpower Iess important than those whicli forin the basis of the class itself; and in the different classes one of theso mothodswili frequently be soland bello adapted to any pi pose of utility than the others. That whicli sues the most naturalarrangement may therelare always be sellowed.
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Tisis division, according to the precessing table os classia scation, includes the laur classes of Νarcotics, Antispa Odios, Tonios, and Astringentsin hese agreeing in the generat stimulant operation they exert On the system, and dissering principalty in the diffusibility and permanetice of acti . They are theresere strictb connected, at least so sae M inseriti a series throti hicli the transition is eastly uaced CHAP. III
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me sollowing are the generat essecis Dona their operation Ιu a moderate dose they incrense the force and frequency of the pulse, promote the secretions, sue Vigour to the bo ly, and 1 use the faculties of the miud, rendering iis conception more vivid and sopcible, and inducing hilarity or in toxicati0n.
These esse is are however OnIy temporary, and aster Sometime sympionis of an opposite kiud malae their appearance ;the pulse not only returus to iis former standurit, hut hecomes more glow, and at the fame time fuli and sost; the respiration is more easy ; ille secretions, excepting that by the Sthin, Me diminishod; pain and inordinate motion, is present, axe alleviated or depressed : there is a generat languor, . SeneSSto motion, and Mulness of Sense : the initul is placid aud in- active; and this state generalty Soon termutates in Steep. This, after continuing sor sonte time, is followed by temp0rary debility, marked by sonae degree of sichneSS, tremorS, anxiety, and oppression. Ιf the dose has beeu large, these sympionis of diministed sense and action are induced, evenwithout any previsus increased action ; or, is a stili largerdose has been giveta, the immediate ConsequenCes are delirium, paralysis, conVulaionS, Coma, aud death. , These e cis Hre considerably diversified, as arising frumdisserent Narcotics. In some, any stimulant operation is scarcely perceptibie, even in a Very moderate dose ; others,
with tbe ii cotio power, possess an acrid quality ; and in al large dose, With the generat essecis above enumeraled, induCel imitation or inflammation of tho stomach, by whicli theiri action is modisied. Some are more apt to induce Siclinessi han others : and illers is reason to bellove ibat there are
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xij upon the stomaeh, wheiace their action is propagated bynerVotis communication to the rest of the system. Thatthey do not aci by being received into the blood, is ovidentsrom the faci, that their cffecis are apparent in generat in a ery Shori time aster theydiave been swallowed; and it hasbeen Dund on dissection immediateb aster these effecti have appeared, that the whole of the quantity administered has remained in the stomach undissolved. Appliud externalty, these medicines osten meri their usual action, though ivitii much Iess sorce. Opium deadens pala, and repreSSes spasmodic muscular action, and this not onlyin the part to whicli it is immediately applied, but in othersmore distant. Severat others of the class have similar ensects ; and their operation in this mode of application, tos,seems to be extended by the medimn of the nerves. Narcotios applied to the muscies of animais, quichen atsrst their action ; but in a very shori time they exhaust allirritability and sensibility. The heari even of coidaloodedanimais is deprived os ali potver of motion by the applicationos a strong solution of opium for a se v minutes. When in-Jected into the blood-vesseis, the animal instantly dies Without convulsions and est the muscies of the body, Volunt y or involuntat , are deprived of the power os contraction. henapplied to wound, they osten affect the generat system, undin iliis case they appear to aci, by being received throughthe divided vetiis into the circulation ; the latcrposition Os aligature on the blood-vcsseis proventing the effeci. In the production of the inecis arising Dona the action ofNarcotics, the bratii secuis to be the organ chiecty affected, andit is in a great incasure frum this nisection that death seonasto follow frona ilicir operation, the diroci action ou the heautheing much less considerablo. I liis has recently bocii more clearly estahlished bi tho expoximents of Mr Er0die. Un