There be also in the same bodie certaine instrumentall partes, compounded and consisting in substance of the similarie, which the bodie doth vse in the executing of the naturall functions, and workinges therof. Now when these similarie partes be so tempered, and disposed, as no one doth excede any other in proportion to ouerrule, but all be as one in consent to preserue: and the instrumentall partes also be so correspondent one to an other, in composition and greatnesse, in number and measure, as nature thorough the temperature of the first, may absolutely vse the perfectnesse of the last, to execute and perfourme without let or stoppe, what appertaineth to the maintenaunce of her selfe: it is called health, and the contrarie, disease, both in the whole bodie, and in euery part therof. In the whole bodie by distemperature of the whole, in some part, by composition, out of place, and disioynted, by greatnes, being to bigge or to small: by measure, being misshapen and fashionles: by number, being to many and needlesse: or to few, and failing. This health whether it be in the middle degre, wherin all executions be complete without any sensible let: and no infirmitie appeareth, that the bodie feeles with any plaine offence: Or if it be in the perfectest degree, which is so seldom, as neuer any saw, bycause of great frailty, and brittlenesse in our nature: it neuer continueth in one estate, but altereth still, and runnes to ruyne, without both speedy and daily, nay without hourely reparation.
The causes which alter, and chaunge it so, be somtime from within the bodie, and were borne with it: sometime from without, and yet not without daunger. From within, the verie propertie and pithe of our originall substance, and matter whence we grew, altereth vs first, which as it beginneth, and groweth in moysture, so it endeth, and stayeth in drynesse, and in the ende decayeth the bodie with to much drynesse, which extreame though naturall withering, we call olde age, which though it come by course, and commaundement of nature, yet beareth it the name, and title of disease, bycause it decayeth the bodie, and deliuereth it to death. From within also, the continuall rebating, and falling awaye of somwhat from the bodie, occasioneth much chaunge, nay that is most cause of greatest chaunge, and killeth incontinent by meere defect, if it be not supplyed.