Royal Society. 385 
themfelves in fuch a manner, as to force out all the aliment, but 
there is left between the Rug^e or folds on the infide of the fto- 
mach, a fufficicnt quantity to be a leaven to the next meal, and 
fo on from time to time: Some entertain a notion, that this fer- 
ment, or principle of fermentation, is in the aliment itfelf, which 
being a congeries of matter coniifting of various parts of a diffe- 
rent nature, is no Iboner incloi'ed in the flomach, and digefled in 
the heat of that, and the adjacent parts, but the more ipirituous 
and fubtile particles are put into motion, and enter upon a fermen- 
tation, both from that warmth and from the difference of their 
natures; and lb by their intefline commotion and the violence 
they offer to thofe parts which oppole the tendency of any of 
them, they break and diflblve the more fblid parts : Again, Ibme 
are of opinion, that this ferment is lupplied from the glands of 
theftomach; and laftly, others, and perhaps with much better 
reafon, contend for the Saliva or fpittle, and make that the fer- 
ment, which principally ferves for the digeftion of the food j for 
the Saliva being mixed with our food in maftication, is with it 
carried downwards into the flomach, where its parts being put into 
motion by a kindly and agreeable heat, they ferment with, and 
agitate firft thole parts of the food, which are moil apt to fer- 
ment therewith ^ and then both conlpire together to break and 
diffolve the grolfer, and more flubborn parts : Galen plainly al- 
lows that the Saliva is concerned in the bufinefs of conco6l:ion, 
tho' he fuppoles the alteration produced by this juice to be made 
in the mouth. 
But according to Dr. Havers's hypothefis, conco6lion is per- 
formed after this manner 5 for the more ealy and effe6lual di- 
geftion of the food, nature has appointed Ibme parts for the 
breaking of our aliment, and reducing whatever is grofs into 
Imaller parts, before it is put upon digeilion j and others to Ibp- 
ply the ferment, by v/hich it is to be diffolvcd and concocled, 
and which, before it is included in the flomach, lervcs to moiflen 
and make it more Ibfr, that it may be more eafily penetrated and 
broken by thole parts, which lerve to divide every morlel into 
fmaller pieces : For the breaking of that part of our food, which 
is not liquid, nature has furnilhed us v/ith teeth, and thofe of 
two Ibrts; ibme are appointed to divide and break off Imaller 
morlels from a larger mals; others are made for the grinding 
thofe morlels into much Ihrialler parts 3 the teeth which ferye to 
break off pieces of a convenient magnitude from a larger mals are 
i of two forts, accommodated to the nature of the lubibance which 
i we eat, and thele are the Licifores and the 'Dented Canini-^ if 
Vol. hi. C c c the 
