That this our speech of sleep and watching, which we now intend, may be more plaine, we will briefely declare, what commoditie or discommoditie they bring, what time and what houre is convenient for both, what the manner of lying must bee, and the choise thereof; what the dreames in sleeping, and what paines or heavinesse and cheerefulnesse after sleepe may portend.

Sleepe is nothing else than the rest of the whole body, and the cessation of the Animall facultie from sense and motion. Sleepe is caused, when the substance of the braine is possessed, and after some sort overcome and dulled by a certaine vaporous, sweete and delightsome humidity; or when the spirits almost exhaust by performance of some labour, cannot any longer sustaine the weight of the body, but cause rest by a necessary consequence, by which meanes nature may produce other from the meate by concoction turned into bloud.

Sleepe fitly taken much helpes the digestion of the parts, because in the time of rest, the heat, being the worker of all concoction, is carryed backe to them, together with the spirits. Neither doth sleepe only give ease to the wearyed members, but also lessens our cares and makes us to forget our labours.

The night is a fit time to sleepe and to take our rest in, as inviting sleepe by its moisture, silence and darknesse. For the heat and spirits in the thick obscurity of night, are driven in and retained in the center of the body; as on the contrary by the daily and as it were friendly and familiar light of the sun, they are allured & drawne forth into the superficies, and outward part of the body; from whence they leave sleeping and begin to wake. Besides also, which makes not a litle, to that opportunity and benefit which wee looke for from sleepe, the night season suffices for the worke of just and perfect concoction. 

Which is one reason amongst many that sleep in the day time may be hurtfull. For wee are wakened from our sleepe by the heat and spirits called forth to the skinne either by the light, or noise in the day time, before that the concoction which was begun be finished. But that sleepe cannot but be light which comes without necessity of sleeping. Wherefore the concoction being attempted, but not perfected, the stomacke is filled with crudities, distended with acide or soure belchings, and the braine troubled with grosse vapours and excrementitious humidities. From whence proceeds paine and heavines of the head, and store of cold diseases. But although sleepe on the night time be wholsome, yet it is fit, that it be restrained within the limits of an indifferent time. For that which exceeds hinders the evacuation of excrements both upwards and downewards: but in the meane time the heate which is neuer idle, drawes from them some portion or vapour into the veines, principall parts and habite of the body, to become matter for some disease. We must measure this time, not by the space of houres, but by the finishing the worke of concoction, which is performed in some, sooner than in other some. Yet that which is longest is perfected and done in seaven, or eight houres. The ventricle subsiding and falling into its selfe and its proper coats, and the urine tinctured yellow, gives perfect judgment thereof. For on the contrary the extension of the stomacke, acide belching, paine of the head, and heavines of the whole body, shew that the concoction is unperfect.

In sleeping we must have speciall care of our lying downe, for first we must lye on our right side, that so the meat may fall into the bottome of our stomacke, which being fleshy and lesse membranous, is the hotter, and more powerfull to assimulate. Then a litle after we must turne upon our left side, that so the Liver with its Lobes, as with hands may on every side embrace the ventricle, and as fire put under a Kettle, hasten the concoction. Lastly, towards morning it will not be unprofitable to turne againe upon our right side, that by this scituation the mouth of the stomacke being opened, the vapoures which arise from the elixation of the Chylus may have freer passage. Lying upon the backe is wholy to be avoided; for from hence the Reines are inflamed, the Stone is bred, Palsies, Convulsion, and all diseases which have their originall from the defluxion into the spinall marrow, and to the nerves taking beginning from thence. To lye upon the belly is not unprofitable for such as have used to lye so, if they be not troubled with defluxions into the eyes; for so the humor will more easily flow into the part affected. But thus the worke of concoction is not a little furthered, because by that forme of lying, not only the inward heate is contained and gathered together about the ventricle, but the encompassing warmenesse of the soft feathers of the bed, aides and assists it.

Neither are the Dreames which we have in our sleepe to be neglected, for by the diligent consideration of these, the affections and superfluous humors which have cheife power in the body are marvailously knowne. For those who have raging choler running up and downe their bodyes while they sleepe, all things to them appeare bright shining, fiery, burning, full of noyse and contention. Those who abound with Phlegme dreame of floods snowes, showers and inundations and falling from high places. Those who are Melancholy dreame of gapings and gulfes in the earth, thicke and obscure darknesse, smokes, caves, and all blacke and dismall things. 

But those whose bodyes abound in blood dreame of marriages, dances, emracings of women, feasts, jests, laughter, of orchards and gardens, and to conclude, of all things pleasant and splendent.

Also we must observe how the patient doth after sleepe, whether more lively and cheerefull, or more heavy, for by the opinion of Hippocrates:

Paine sleepe ensuing, an ill disease doth show;

But if sleepe profit bring, no harme from thence will flow.

And as sleepe so watching, if it exceede measure, is hurtful; for it hurts the temperature of the braine, weakens the senses, wastes the spirits, breeds crudities, heavinesse of the head, falling away of the flesh, and leanenesse over all the body, and to conclude, it makes ulcers more dry, and so consequently rebellious, difficult to heale, and maligne. There are many other things may be spoken of sleepe and watching, but these may suffice a surgeon.