Secondly, (as is argued by _Aristotle_ against the _Pythagoreans_) whatsoever properly nourisheth before its assimulation, by the action of natural heat it receiveth a corpulency or incrassation progressional unto its conversion; which notwithstanding cannot be effected upon air; for the action of heat doth not condense but rarifie that body, and by attenuation, rather then for nutrition, disposeth it for expulsion.
Thirdly, (which is the argument of _Hippocrates_) all aliment received into the body, must be therein a considerable space retained, and not immediately expelled. Now air but momentally remaining in our bodies, it hath no proportionable space for its conversion; only of length enough to refrigerate the heart; which having once performed, lest being it self heated again, it should suffocate that part, it maketh no stay, but hasteth back the same way it passed in.
Fourthly, The use of air attracted by the lungs, and without which there is no durable continuation in life, is not the nutrition of parts, but the contemperation and ventilation of that fire always maintained in the forge of life; whereby although in some manner it concurreth unto nutrition, yet can it not receive the proper name of nutriment. And therefore by _Hippocrates_[SN: De Alimento.] it is termed _Alimentum non Alimentum_, a nourishment and no nourishment. That is, in a large acception, but not in propriety of language; conserving the body, not nourishing the same; nor repairing it by assimulation, but preserving it by ventilation; for thereby the natural flame is preserved from extinction, and so the individuum supported in some way like nutrition.
And though the air so entreth the Lungs, that by its nitrous Spirit doth affect the heart, and several ways qualifie the blood; and though it be also admitted into other parts, even by the meat we chew, yet that it affordeth a proper nutriment alone, it is not easily made out.
Again, Some are so far from affirming the air to afford any nutriment, that they plainly deny it to be any Element, or that it entreth into mixt bodies as any principle in their compositions, but performeth other offices in the Universe; as to fill all vacuities about the earth or beneath it, to convey the heat of the sun, to maintain fires and flames, to serve for the flight of volatils, respiration of breathing Animals, and refrigeration of others. And although we receive it as an Element, yet since the transmutation of Elements and simple bodies, is not beyond great question, since also it is no easie matter to demonstrate that air is so much as convertible into water [SN: _Wherein Vapour is commonly mistaken for air._]; how transmutable it is into flesh, may be of deeper doubt.