I. The Practice of Purging and Vomiting Medicines, according to Dr. Cockburn's Solution of his Pro⯑blem; with Tables ſhewing their Doſes in particu⯑lar Ages and Conſtitutions. Inſcrib'd to the Learned Dr. Garth, F. R. S. by W. Cockburn, M. D.

BY my Solution of the Problem for determining the due Doſes of Purging and Vomiting Medicines, Phil. Tranſ⯑act. No. 303. in all their Caſes, it is manifeſt in general, Poſtul. that theſe Medi⯑cines operate either upon the account of their being mix⯑ed with the Blood, Schol. or by their ſtimulating the Stomach and Guts: 2. That this their Operation is more or leſs according to the Quantity and Thickneſs of Blood, h.e. Cor. 1. a greater Quantity, and the thickeſt Blood require the greateſt Doſes: And 3, Prop. 1. that when the Quantities of Blood are the ſame, the Doſes of Purging and Vomiting Medicines are in a duplicate proportion of the Bloods thickneſs. As alſo, that in every caſe theſe Doſes muſt be in a proportion compounded of the Quantity of Blood and thoſe Squares of its thickneſs. Prop. 2.

Now ſince the Operations of Purgative and Vomitive Medicines depend ſo much on the Quantity and Viſcidity of the Blood, Why the Do⯑ſes of theſe Medicines ſo hard to be found. which have not been duely conſider'd be⯑fore; it is no wonder that the Practice of Phyſick in theſe Evacuations has been ſo uncertain, and that the moſt ex⯑pert Phyſicians, from their moſt accurate Obſervations, could never determine the true Doſes of Medicines, which alter ſo much according to the various Subjects they work upon; they not being acquainted with the true Method of determining either the quantity of the Blood, or the degrees of its thickneſs.

Becauſe Experience is equally the Foundation and Touchſtone of all reaſoning in Phyſick, we will here ſub⯑mit our Solution to common Obſervations, and try whe⯑ther every thing propoſed in it, does not exactly anſwer Matters of Fact, and the viſible Operations of Na⯑ture.

Firſt then, The different effects of theſe Medicines upon the ac⯑count of their [...] it plainly follows, that theſe Medicines al⯑ways purge beſt and moſt conſtantly in a liquid form; becauſe they are more eaſily convey'd into the Blood, and can ſtimulate more parts, and that upon the account of this their Fluidity; whatever may be the way that Purges and Vomits work, or whatſoever their Nature may be. This explains very eaſily a very common Ob⯑ſervation, hitherto very difficult to Phyſicians, about the different Operation of the ſame Medicine in different forms: Why, viz. the Infuſion of a due quantity of a Purging Medicine produces its effects ſooner and more conſtantly than a like quantity of the ſame Medicine in a Powder, tho' ſtill more conſtantly in a Powder than a Bolus, tho' ſtill ſooner and more conſtantly in a dry Bo⯑lus, than if it be given in Pills made into that form with Gums that do not purge; and this difference in Purging ſhall even be notable, according to the diſſolubility of the Gums.

From whence it follows, that the Evacuation made by ſuch Medicines, is in proportion to the quantity of thoſe Medicines that happens to be diſſolv'd, and not to the quantity adminiſter'd.

Secondly, Their effects different, be⯑cauſe of the different thickneſs of Blood. That purging by Draughts is the moſt ex⯑cellent form, and will always have the moſt conſtant effect.

The next Conſideration is, that a certain quantity of any purging Medicine affects us after a different manner, according to the different Quantity and Conſtitution of the Blood, or its thickneſs, and it was ſhewn in the So⯑lution, that if its thickneſs were the ſame, the Doſe [3]ſhould always be as its Quantity, but the Blood differing likewiſe in thickneſs, the Doſes of Purging and Vomiting Medicines muſt be augmented on account of its thickneſs. This is perfectly well confirm'd by daily experience; where we find, that People ſick with a manifeſt thick⯑neſs of Blood, as in Dropſies, the Jaundice, &c. take far greater Doſes than they did at any other time when they were not ſick, or in that manner.

By a further Diſquiſition into this matter, we find that the Doſes muſt not only be greater where the thickneſs of Blood is greater; but that they muſt be encreas'd in a duplicate proportion of their Viſcidity. This is evident by the Tables in Caſſia. viz. 9:83::4:3ʒ, 1 ℈, 13⅓ gr. and therefore alternando 9:4::8 ʒ:3 ʒ, 1 ℈, 13 ⅓ gr. Therefore the Doſes are as the Squares of the Conſtitutions. So likewiſe 9:8 ʒ::16:14 ʒ, 13 ⅓ gr. and alternando 9:16::8 ʒ:14 ʒ, 13 ⅓ gr. h. e. the Doſes are as the Squares of the Conſtitutions.

The ſame is true in any other Conſtitution beſides the mean: For Example, in the loweſt and higheſt 4:16:: 213 ⅓ gr: 853 ⅓. So that by this means we are not only led directly to a right uſe of theſe Medicines, and are able to find the true cauſe why the ordinary Doſes produce ſo very different effects in different Conſtitutions; but like⯑wiſe, A Problem. The Quantity of Blood in any Perſon being given together with the ordinary and extraordinary effect of a Doſe of a Purging Medicine, the Change of that Perſons Conſtitution, and the Nature of that Change may be deter⯑min'd.

It cannot but be a great ſatisfaction to the mind to find a Doctrine founded on a few ſimple Experiences leading us into the cauſe of many more that are very complext, This Doctrine true becauſe conform to Nature. difficult, and obſcure; which is ſufficient to prove its conformity to Nature. But my preſent endeavour being to rectify the common Practice of theſe Medicines by this Doctrine, I ſhall frame, by this Method, Tables of the [4]Purging and Vomiting Medicines in preſent uſe; better adapted to Experience than are hitherto to be found.

The Method of framing ſuch Tables, How they are made. is by ſetting off the practicable Conſtitutions in the different Ages that I have obſerv'd to take notable Quantities of Purging and Vomiting Medicines; ſo that by comparing theſe Conſti⯑tutions with the Ages, we have the different Doſes in all thoſe caſes, which is all that is requir'd for a better pra⯑ctice; tho' a more proper occaſion may produce a more nice and exact diviſion of Conſtitutions, very much to the advantage of the Practice of Phyſick in all Diſeaſes.

The Ages wherein theſe different Doſes are taken, I find to be four; when a Man is about 16 or 20 Years of Age, and weighs about 12 Stone, he then takes the com⯑mon Doſe: One of nine Years takes three quarters of that; one of ſix the half, and one of three Years a quarter. Moreover, [...] p. 51. Bibli⯑oth. Anatom. p. 1124. T [...]. 2. it having already been ſhewn, that the nota⯑ble healthy Conſtitutions are but three, as alſo the nota⯑ble Pulſes of each of theſe: Let then theſe Conſtitutions be as 2, 3, 4. That of the moſt fluid Blood as the firſt number, and ſo on; in that caſe, the Doſe of any Perſon will be found by multiplying the common Doſe for his Age into the Square of his Conſtitution and dividing by the Square of the middle Conſtitution. For inſtance, If ℥j. Caſſioe is the common Doſe, or the Doſe of the middle Conſtitution, ʒiij. ℈j. and gr. 13 ⅓ is the Doſe of the firſt Conſtitution, and ʒxiv. gr. 13 ⅓ that of the groſſeſt or laſt Conſtitution; and ſo proportionably for every Medicine in all the Ages, as appears by the Tables.

This Method ſeems to anſwer ſo exactly, Only excep⯑tion. that there is not any thing neceſſary beſides, except a Perſon is more Looſe or Coſtive than ordinary (which may be known from the Patient or otherways) it is to be reputed the ſame, as if he had taken an equivalent quantity of a Me⯑dicine proper to produce theſe effects. Any Phyſician, [5]who has conſider'd this caſe in ſome People after Flux⯑ing, will allow the juſtneſs of this Exception.

As Vomiting Medicines have the ſame common Doſes with thoſe that Purge, The Doſes of Vomiting Medicines. they admit alſo of the like divi⯑ded Doſes; which, therefore may be found by the ſame Tables. Only, as People that are more Coſtive than or⯑dinary require a proportionable greater Doſe of a Purg⯑ing Medicine: So they require their Doſe of a Vomiting Medicine to be conſiderably leſs, as is very very well known in hot Countries.

But it muſt be obſerved, that in the Tables, Note [...]. Age ſtands Inſtead of Quantity of Blood; becauſe they encreaſe pret⯑ty equally, and it makes the practice more eaſie to ſuch as are not accuſtom'd to Weights and Numbers.

The more Skilful are deſir'd to obſerve, that the mean Ages, [...].multiply'd into the mean Conſtitutions, give Doſes more nicely.