A system of materia medica and pharmacy [electronic resource] : including translations of the Edinburgh, London, and Dublin pharmacopoeias, in two volumes

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Introduction

teria Medica . . l- , II. - Pharmaceutical operatioris . 74

PART II.

CHAP. I. Preliminary Observations . 9 - II. Ofthe operations and olassi atton o Medicines...t03

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inent of disease, may be presented under two potuis of View. Undex one, the symptoms of disenses are described, theid Causes are investigated, tho iudicati s are deIivered by whichtheir cure is to he attempted, and the remedies are enumera ted by whicli these indications are to be suis illed. v licii this method is sellowed, a prerious knowlei e is supp0ged os the natu es histo , properties, and medicines powers of the Substances employed as remedies; and they are no sarther subjecta os attention, than to polat out their applications io particular caSes, and the cautions whicli, storii peculiarity of circumstances, require to be attended to in ili te adminis

Eut the subject may alqo he presented under another aspect. The Sympionis of disenses, thoir causes, and indications os cure, may be supposed to he known, and the remedies thenaselves become principalty the objecis os study,-their natural characters, their sensibie qualities, thoir effecison the living system, thc theory of iliciae action, and their applications to the trestiment of morbid affections, sorining 80 many subjects of description or investigation. This constitutes the depretinent of MATERIA MEDICA,-iuiderStood in the most extensive signification of the terna.

The medicinal po vers of natural hodies are coimected willa their chemicat constitution ; they frequently reside, not in the entire mattex composing them, but in principies capsthle

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vantagos. When given in combination too, these subglancesare tiable sonaetimes to aci on each other, and Dona thochanges arising froin these mutuat actionS, to suffer alterations in their properties. Henco arises the necessity of astri ' attention to their chemicat composition ; and a de scription of their constituent principies, and of their chemices relations, so far at least as these influence their actions remedioes, belongs to this departinenti of Medicine. Wo arealso osten able, b chemical combinations, to modisy the powers of these Substances, to give them moro activi , undeven by the production os new compotin is, to obtain rem

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nectod with their medicinal properties and applications. It comaecis the doctrines of Materia Medica and Pharmacy, and fornas a proper inti duction to the study of each ; an exposition os iis principies being necessary to the history of ilio articles of the Materia Medica, and be g not less indispens te in explaining the operations os Pharmacy. It includes two subjects ; s rat, the analysis of bodies, so far as relatos totheenumeration of theiae constituent principies; anii, Secondse, the generes operations to Whicli they are subjected in thoid

preparation as remedies.

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Γng ultimato object of chemicat investigations, is to disco- ver the composition os hodies ; and the result of these investigations is the reducing them into two classes, those xviii hare Simple, and th'se whioli are Compo d. The formorare Such as consist of paris perfectly Mike ; the most minute les into ita a Simple hody can he resolvia, Petaining ali iis essentia I p perties, and betas Similis to euch other The lalter cum o the contra , he resoluta into si Stanc different in theis qualities Dom Och Other, and Dona the compound whicli they forna. It is froni the union os simple substances that Compo titare modi ed. When two Simple hodies are placed imiter those ch cumstances whicli savom tho exortion of their m tu es retinaclion, si unite and lam a conloimd, haVing p Culiar properties. These compo iis are fatether capable of combining 1vith other simple hodieri or xviis each other,

which Hvoes rim to a series of dies Stili more extensive and thois again axe c able of now combinations, or os Suchiutimate mixtures With each oti to form many peculiarsi clances. There are thus producta, fram a se simplo subnam' , ali the producis of nature, alia ad those Whichare the insulis of the operations os ari.

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The generat process by Whicli these objecis uro attained, is termed, in the lingua ge of Chemistry, Analysis. It is merely the separation os a compound hody into iis constituent paris, and is essected either by the agency of hcat, or

The analysis froni the applicatiun of heat, differs accord- ing to the composition of the body unalysed. Is a compo d, consisting of two simple substances, be exposcit to heat, it in many ca8eS happens, that the mutuat attraction by whicli iis

principies Π ere united Censes, and a decomposition or sep

ration of these principies tinos pluce. This is an ex ple os pure analysis no change being produced, but mei 'ely thesi aration of the component paris of the Compouaad, so thateuch is obtained in iis original state. An analysis more complicated is that ultore severat substances are combined togetlier, in such a manner that their attractions are aeeciprocatly balanced, and ono compoQid is

Rimed. When a compo d of this tanti is exposed to .a hi temperatiu)e, this halance is frequently subvertud, and it suf- sors decori osition. Lut iis constituent principies, instead Di passing os Γ pu e, inter into nexu combinations v illi euchother, and other compotin is, cach of ix hich may be cotilected, and in iis tum analysed. It is in this manner iliat vegetable and animal substances are acted on by liciat: the producis usibi ded by their analysis are not such RS yxe-existed in them, but are compotin is sormed diu ing the docomposition, by ne v combinations of their ultimato constituent principies. Illis is What hvs hcenaiam od Fulge or Complicated Ana lusis.

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OF THE GENERAE PRINCIPLES. Chemicat Analysis is also essected by the exertion os a Superior attraction. Is a compound bo placod successivoly with

disserent substances in siluations favourable to the operationos chemicat action, one or other of them may exert a S C-rior attraction to either of iis component paris ; a decomposition will be produced, and Dona the producis the constituent principies of the compotinil, as well as their proportions may be determined.

A S compomid substances can combine together so as tolam a new Compo d, it is Obvious, that this compound maybe resolved either into the immediate principies si in lire union of whicli it has been formed, or into those of whichthese consist. It is necessa , ilieres ore, that these Shouldhe distinguished. The former are accord Hy named the Proximate Pirincipies of a compound ; the lattex the ULtimate Principies. The prorimate principies are Com- pomids; the ultimate principies are the elementa os these con pomids and tho resulis of analysis are extremely different, according as One or other Os these is obtained. When by analysis the constituent principies of a body have been obtained, they may osten be combined again, SO toreproduce the substance analysed. This operation is named Chemicat Synthesis, and, wheu it can be effected, is the su est proos of the acciuacy of the analysis. It is seldoin that itcan be applied to those compouuds whicli suffer a coryplicat-od analysis ; and heiace tho composition Os vegetable or animal Si StanceS Can scat'Cely ever bc Confirmed by a synthetic experiment. In analysing the various producis of naturo, Wo arri 'e ultimately at substruices whicli ive are unal le to decompose,

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babie, stat ali the substances Whicli are 3 et known to tus inni bo compotivds, and that a more relined chemisti may disco ver theiu composition. Γntit this bo accomptished, hori ever, they are regariled as simple, and they are So Mith regard atteast to otu ou ledge of them. As the ultimate principleg, therelare, of ali analysis, they are si si to be considerod in procee ling to the generat analysis of the urticles of the Maiateria Medica. Os these hodies, OXYoges is tho most importaui. There

Mith a se exceptions, indeed, ait the productions os natureare either cap te os combining, or are Hready combinod withthis principie, and the developement of iis agencies constitutes

ille most extensive and important part of Chemicat science. Oxygen, Phen unCombined, niways exisis in the gaseous state : and iis descriptive Characters are there re talaen fromit as it exigis in the aeriat sorin. Lilae other gases, it is invisibie and elastic ; iis Specisio gravity is vallier grenter than that of atmosplieric air; it is absorbed by water, but in a verysmal l proportion. Tlio distinguishing properties of OXygen gus are those Ofsupporting respiration and combustion. An animal lives longor in this uir than it does in any other; and combustionis it is more vivid, and continues longer. It is the only air, inducit, 3 hicli, Strictiy Speaking, caii Support Cither of illese processes ; otheae acrisorin fluids Eoing so only frona the oxygen they contain. Iis capacity of supporting combustion is more particularly 10 he a sumed us iis characteristic chemicui property ; combustiou heing n illiing but the combivation of Oxygen ivitii combustibio hodies, accompunicil With the emission of heatniad light. It also si e plenily, however, enters into combina-

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OF THE GENERAL PRINCIPI Estion dithout the phenomena os combustion bcing apparent, more especialty when the absorption os it tines place flowly, or whon it is transferred Dona a compomid in v hicla it oxisisto mollier substance. The combination os a body with oxygen is termed Oxygenation, or OXidation. The producis of this combination have either certain common properties, be-

longing to a class os ci emicat agenis long distinguished by the appellation os Acids ; or they are d titute of these properties, and they are then denominat ed OXides. Oxygen forma one- urth pari os rei mospheric air; and itis principalty on iis ageno that the many chemicat changog paroduced in hodies by that uir cleptariis. Combined with another elastic fluid, hydrogen, in the proportion of 85 paris tol 5, it forins Water, the substance whicli has the most exten- Sive operation in promoting chemices action by the fluidity it

communicates, and whicli more directly produces many -- portant chemicat changes, by inording oxygen to hodies. oxygen erisis too as a constituent principio os acidf, and commificates to them their energy of action. It is also An ingredient in the composition of the aikalis and Catilis, aud it is theres ore the principie of aries ity as weli as of acidity. With ait tho metuis it combinus, communicating to them agi eater susceptibility of chemicat action, and greater activityin their relati0n to tho living system ; and it eXistS aS n constituent patri of nearly ad the vegetable and animal producis Helice no principie is more extensively diffused, and nunc has a more mathed lassuence in the combinations into whicli it