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that kind of colliquation is not made either by an overdry heat, or an over-moist heat: for over-moisture doth somewhat extinguish the heat; as we see that even hot water quencheth fire ; and over-dry heat slutteth the pores : and therefore men will sooner sweat covered before the sun or fire, than if they stood naked: and earthen bottles filled with hot water do provoke, in bed, a sweat more daintily than brick-bats hot. Secondly, hot water doth cause evaporation from the skin ; so as it spendeth the matter in those parts under the water, before it issueth in sweat. Again, sweat cometh more plentifully, if the heat be increased by degrees, than if it be greatest at first, or equal. The cause is, for that the pores are better opened by a gentle heat than by a more violent; and by their opening the sweat issueth more abundantly. And therefore physicians may do well, when they provoke sweat in bed by bottles with a decoction of sudorific herbs in, hot water, to make two degrees of heat in the bottles ; and to lay in the bed the less heated first, and after half an hour, the more heated.
707. Sweat is salt in taste; the cause is, for that that part of the nourishment which is fresh and sweet, turneth into blood and flesh; and the sweat is only that part which is separate and excerned. Blood also raw hath some saltness, more than flesh ; because the assimilation into flesh is not without a little and subtile excretion from the blood.
708. Sweat cometh forth more out of the upper parts of the body than the lower ; the reason is, because those parts are more replenished with spirits ; and the spirits are they that put forth sweat: besides, they are less fleshy, and sweat issueth (chiefly) out of
the parts that are less fleshy, and more dry; as the forehead and breast.
709. Men sweat more in sleep than waking; and yet sleep doth rather stay other fluxions, than cause them; as rheums, looseness of the body, &c. The cause is, for that in sleep the heat and spirits do naturally move inwards, and there rest. But when they are collected once within, the heat becometh more violent and irritate ; and thereby expelleth sweat.
710. Cold sweats are (many times) mortal, and near death; and always ill, and suspected : as in great fears, hypochondriacal passions, &c. The cause is, for that cold sweats come by a relaxation or forsaking of the spirits, whereby the moisture of the body, which heat did keep firm in the parts, severeth and issueth out.
711. In those diseases which cannot be discharged by sweat, sweat is ill, and rather to be stayed; as in diseases of the lungs, and fluxes of the belly : but in those diseases which are expelled by sweat, it easeth and lighteneth ; as in agues, pestilences, &c. The cause is, for that sweat in the latter sort is partly critical, and sendeth forth the matter that offendeth ; but in the former, it either proceedeth from the labour of the spirits, which sheweth them oppressed ; or from motion of consent, when nature, not able to expel the disease where it is seated, moveth to an expulsion indifferent over all the body.
Experiment solitary touching the glow-worm. 712. The nature of the glow-worm is hitherto not well observed. Thus much we see; that they breed
chiefly in the hottest months of summer; and that they breed not in champaign, but in bushes and hedges. Whereby it may be conceived that the spirit of them is very fine, and not to be refined but by summer heats : and again, that by reason of the fineness it doth easily exhale. In Italy, and the hotter countries, there is a fly they call lucciole, that shineth as the glow-worm doth ; and it may be is the flying glow
But that fly is chiefly upon fens and marshes. But yet the two former observations hold : for they are not seen but in the heat of summer; and sedge, or other green of the fens, give as good shade as bushes. It may be the glow-worms of the cold countries ripen not so far as to be winged.
Experiments in consort touching the impressions which
the passions of the mind make upon the body. 713. The passions of the mind work upon the body the impressions following. Fear causeth paleness, trembling, the standing of the hair upright, starting, and skriching. The paleness is caused, for that the blood runneth inward to succour the heart. The trembling is caused, for that through the flight of the spirits inward, the outward parts are destituted, and not sustained. Standing upright of the hair is caused, for that by shutting of the pores of the skin, the hair that lieth aslope must needs rise. Starting is both an apprehension of the thing feared, (and in that kind it is a motion of shrinking,) and likewise an inquisition, in the beginning, what the matter should be, (and in that kind it is a motion of erection); and therefore when a man would listen suddenly to any thing, he starteth ; for the starting is an erection of the spirits to attend. Skriching is an appetite of expelling that which suddenly striketh the spirits : for it must be noted that many motions, though they be unprofitable to expel that which hurteth, yet they are offers of nature, and cause motions by consent; as in groaning or crying upon pain.
714. Grief and pain cause sighing, sobbing, groaning, screaming and roaring, tears, distorting of the face, grinding of the teeth, sweating. Sighing is caused by the drawing in of a greater quantity of breath to refresh the heart that laboureth ; like a great draught when one is thirsty. Sobbing is the same thing stronger. Groaning, and screaming, and roaring, are caused by an appetite of expulsion, as hath been said : for when the spirits cannot expel the thing that hurteth, in their strife to do it, by motion of consent they expel the voice. And this is when the spirits yield, and give over to resist : for if one do constantly resist pain, he will not groan. Tears are caused by a contraction of the spirits of the brain ; which contraction by consequence astringeth the moisture of the brain, and thereby sendeth tears into the eyes. And this contraction or compression causeth also wringing of the hands ; for wringing is a gesture of expression of moisture. The distorting of the face is caused by a contention, first to bear and resist, and then to expel; which maketh the parts knit first, and afterwards open. Grinding of the teeth is caused likewise by a gathering and serring of the spirits together to resist ; which maketh the teeth also to set hard one against another. Sweating is also a compound motion, by the labour of the spirits first to resist; and then to 715. Joy causeth a cheerfulness and vigour in the eyes, singing, leaping, dancing, and sometimes tears. All these are the effects of the dilatation and coming forth of the spirits into the outward parts; which maketh them more lively and stirring. We know it hath been seen that excessive sudden joy hath caused present death, while the spirits did spread so much as they could not retire again. As for tears, they are the effects of compression of the moisture of the brain, upon dilatation of the spirits. For compression of the spirits worketh an expression of the moisture of the brain by consent, as hath been said in grief. But then in joy, it worketh it diversely ; viz. by propulsion of the moisture, when the spirits dilate and occupy more
716. Anger causeth paleness in some, and the going and coming of the colour in others : also trembling in some: swelling, foaming at the mouth, stamping, bending of the fist. Paleness, and going and coming of the colour, are caused by the burning of the spirits about the heart; which, to refresh themselves, call in more spirits from the outward parts. And if the paleness be alone, without sending forth the colour again, it is commonly joined with some fear; but in many there is no paleness at all, but contrariwise redness about the cheeks and gills ; which is by the sending forth of the spirits in an appetite to revenge. Trembling in anger is likewise by a calling in of the spirits ; and is commonly when anger is joined with fear. Swelling is caused, both by a dilatation of the spirits by over-heating, and by a liquefaction or boiling of the humours thereupon. Foaming at the mouth is from the same cause, being an ebullition. Stamping, and bending