Foreign Vegetables. 381 
They who ufe opiate Medicines for a long Time, 
often find that the fame Dofe which in the Begin- 
ning was fufficient to induce Sleep, after fomeTime 
becomes ineffectual ; and that a larger Dofe is re- 
quired, or alfo, to have the defired Effedt, that it 
muff be daily augmented. Now this happens, be- 
caufe the Blood, by the firft Doles of the Medicine, 
acquires a certain Degree of Fluidity, which the 
fame Dofe is not able to increafe. For the fuper- 
fluous Recrements of the Blood having been caff 
off by Sweat or by Perfpiration, the Bulk of the 
Blood is diminifhed, fo that it does not afterwards 
diftend the Arteries fufficiently to comprefs the 
Nerves and caufe Sleep. To fwell the Arteries to 
an equal Amplitude a greater Quantity of Opium 
is required, whereby the Mafs of Blood may be 
further diffolved and rarefied ; and fo more and 
more, until it hath acquired the utmoft Degree of 
Fluidity poffible : And then larger Dofes of Opi- 
um, reiterated and increafed, are no longer able to 
procure Sleep. 
Here it may be demanded, what are the Princi- 
ples, by which Opium produces this remarkable 
Diffolution and Expanfion of the Blood ? To which 
I anfwer, that Opium is compounded of Salts, both 
acid and alkaline-urinous, and of a thick Sulphur 
greatly condenfated, but capable of the greateft 
Divifibility and Expanfion : And I think, that its 
foporiferous Virtue is not owing fo much to the 
Salts as to the Sulphur *, fince we obferve, that 
Bodies replete with a Sulphur of the like Sort oc- 
cafion Sleep, as Saffron, Nutmeg, Caftor, &c. 
Now, Opium and the foporiferous Aromaticks, 
when taken into the Stomach, are diffolved by its 
fermentative Liquor, and put into Fermentation. 
Their narcotick Sulphurs half expanded by this 
Fermentation are carried to the Mafs of Blood; 
where 
