384 MEMOIR S of the 
nicd but that oil of vitriol will difTolve fle/h and reduce it 
to a pulp; yet it is not to be fuppoled, that the fibres of the fto- 
mach can bear any fuch ftrong and corroding acid, without being 
iniured in its tone, and without being effe6ted with great and ex- 
traordinary pains j neither does fuch a menftruum, tho' it will di- 
geft fome bodies, feem capable of diffolving fo great a variety of 
things as we eat, efpecially when a great many of them are of a 
contrary nature to each other : Some will have the menftruum to 
be a nitro-aereous fpirit, fubtile, and yery penetrating, and in- 
cluded in its proper vehicle, which, being in its own nature apt 
to penetrate the mafs of the aliment, difFufes itfelf thro' tlie 
whole, and breaking the cohefion of the moft folid parts, dif. 
folves their compages : By others, it is thought to be fome laline 
juice in the ftomach, by which the parts of the aliment are di- 
vided and diffolved, and thofe fit for nourifhment volatilized : 
Laftly, there are fome, who fuppofe, that digeftion is performed 
by means of a ferment, which, when mixed with the aliment, 
excites in the mafs an intefiine motion 5 and the different and 
contrary motions or tendencies of the parts, by making fome kind 
of coUifion, gradually break off particles from the groffer and 
more folid parts, till they are fo attenuated, as to be apt to mix 
more equally with the fluid parts, and with them ccnftitute one 
foft or chylous fubftance; but thefe alio differ, either as to 
the nature of this ferment, or the manner wherein it is fup- 
plied ^ for fc)me take it to be the remains of the food that was 
laft di^efted, which having lain fome time in the ftomach, after 
the reft is carried down into the inteftines, contrail: an«acid or 
fome fuch quality, and become fo altered as to partake of the na- 
ture of a leaven 5 and this leaven being a part of the food, which 
has been already digefted, is fo foft and liquid, as to be capable 
of mixing with the alim.ent, which is next taken into the fto- 
mach, and being agitated therewith by the repeated preffures of 
the diaphragm, liver and abdominal mufcles upon the ftomach in 
refpirat'ion, diffufes itfelf thro' the whole mafs, and being mixed 
with it like leaven, or yeaft added to new wort, ^c puts it into 
a ftate of fermentation; and by this fermentation, or by theex- 
panfion of the ferment, and the more fubtile parts, which are 
firft put into motion thereby, thofe parts, which are more Iblid, 
and with which they are intermixed, are rent and divided and 
attenuated in iuch a manner, as to become a foft and pulpous 
matter; and altho' the greateft part of the food, that is thus 
broken and concocted, is "by the contraflion of the fibres of the 
ftomach pieffed into the tDiwdemm^ yet they do iiot contra^ 
them- 
