But with Man it is performed otherwise; for in regard of site he alters his natural posture and swimmeth prone; whereas he walketh erect. Again, in progression the arms move parallel to the legs, and the arms and legs unto each other; but in natation they intersect and make all sorts of angles. And lastly, in progressive motion, the arms and legs do move successively, but in natation both together; all which aptly to perform, and so as to support and advance the body, is a point of Art, and such as some in their young and docile years could never attain. But although swimming be acquired by art, yet is there somewhat more of nature in it then we observe in other habits, nor will it strictly fall under that definition; for once obtained, it is not to be removed; nor is there any who from disuse did ever yet forget it. Secondly, That persons drowned arise and float the ninth day when their gall breaketh, is a questionable determination both in the time and cause. For the time of floating, it is uncertain according to the time of putrefaction, which shall retard or accelerate according to the subject and season of the year; for as we observed, _Cats_ and _Mice_ will arise unequally, and at different times, though drowned at the same. Such as are fat do commonly float soonest, for their bodies soonest ferment, and that substance approacheth nearest unto air: and this is one of _Aristotles_ reasons why dead _Eels_ will not float, because saith he, they have but slender bellies, and little fat. [Sidenote: _Why drowned bodies float after a time._] As for the cause, it is not so reasonably imputed unto the breaking of the gall as the putrefaction or corruptive firmentation of the body, whereby the unnatural heat prevailing, the putrifying parts do suffer a turgescence and inflation, and becoming aery and spumous affect to approach the air, and ascend unto the surface of the water. And this is also evidenced in Eggs, whereof the sound ones sink, and such as are addled swim, as do also those which are termed hypenemia or wind-eggs; and this is also a way to separate seeds, whereof such as are corrupted and steril, swim; and this agreeth not only unto the seed of plants lockt up and capsulated in their husks, but also unto the sperm and seminal humour of Man; for such a passage hath _Aristotle_ upon the Inquisition and test of its fertility.