Hippocrates in his fourth booke of Aphorismes, the fift, hath these words:  Sub canicula, & ante caniculam difficiles sunt purgationes. That is, under the canicular, or dog-star, and before the dog-star, purgations are painfull and difficill.  This is all that is there said of them, or brought against them for that season, or time of the yeare.  A great stumbling-blocke against which many have dashed their feet, and knockt their shinnes, and a fearfull scar-crow, whereat too many have nicely boggled.  Here you doe not find or see purging medicines to bee then prohibited, or forbidden to be given at all (much lesse all other physicke) but onely said to be difficill in their working:  partly because (as all expositors agree) nature is then somewhat enfeebled by the great heat of the weather; partly because the humours being then, as it were, accended are more chaffed by the heat of the purging medicines; partly, and lastly, because two contrary motions seeme then to be at one and the same time, which may offend nature; as the great heat of the weather leading the humours of the body outwardly to the circumference thereof, and the medicine drawing them inwardly to the center.  All which circumstances in our cold region are little, or nothing at all (as formerly hath beene mentioned) to be regarded.  For as Jacobus Hollerius, a French Physitian, much honoured for his great learning and judgement, hath very well observed in his Comment upon this Aphorisme; Hippocrates speaketh here onely of those purging medicines, which are strong, and vehement, or hot and fiery; and that this precept is to take place in most hot Regions, but not in these cold Countries, as France, England, and the like.

Over and beside all this, those churlish hot purging medicines, which were then in frequent use in Hippocrates his time, and some hundred of yeares after, are now for most part obsolete, and quite growne out of use, seldom brought in practice by Physitians in these dayes; because we have within these last six hundred yeares great choice and variety of more mild, benigne, and gentle purgatives found out by the Arabian Physitians, which were altogether unknowne unto the ancients, to wit, Hippocrates, Dioscorides, Galen, &c. which have little heat, and acrimony, many whereof are temperate, and divers cooling, which may most safely be given either in the hottest times and seasons of the yeare, or in the hottest diseases.  Let us adde to these the like familiar and gentle purging medicines more lately, yea, almost daily newly found out since the better discoveries of the East and West Indies.  So that henceforth let no man feare to take either easie purgatives, or other inward Physicke, in the time of the canicular, or dog-dayes.