For thirst does not call for a superfluity of moisture, but only for so much as sufficeth Nature; and therefore, though a man had plenty of disagreeable and unnatural moisture, yet he wants still, for that stops the course of the natural, which Nature is desirous of, and hinders a due mixture and temperament, till it be cast out and the pores receive what is most proper and convenient for them.
Moreover, a fever forces all the moisture downward; and the middle parts being in combustion, it all retires thither, and there is shut up and forcibly detained.

And therefore it is usual with a great many to vomit, by reason of the density of the inward parts squeezing out the moisture, and likewise to thirst, by reason of the poor and dry state the rest of the body is in.

But after the violence of the distemper is once abated, and the raging heat hath left the middle parts, the moisture begins to disperse itself again; and according to its natural motion, by a speedy conveyance into all the parts, it refreshes the entrails, softens and makes tender the dry and parched flesh.

Very often also it causes sweat, and then the defect which occasioned thirst ceases; for the moisture leaving that part of the body wherein it was forcibly detained, and out of which it hardly made an escape, retires to the place where it is wanted.

For as it fares with a garden wherein there is a large well,--if nobody draw thereof and water it, the herbs must needs wither and die,--so it fares with a body; if all the moisture be contracted into one part, it is no wonder if the rest be in want and dry, till it is diffused again over the other limbs.