"Scaliger, Fernelius, and others lay less weight on the extraordinary endowments of the blood and imagine other spirits to exist, aërial or ethereal or composed of substance both ethereal and elemental, constituting an innate heat more excellent and more divine, as it were; and these spirits they believe to be the soul's most immediate instrument, the fittest for every use. They rely especially upon this argument, viz.: that the blood, being composed of elements, can exert no activity beyond the powers of the elements or of bodies consisting of a mixture thereof. Therefore, they imagine a spirit, another innate heat, of celestial origin and nature, to wit: a body most simple, most subtile, most fine, most mobile, most swift, most clear, ethereal, and sharing in the quintessence. Nowhere, however, has any such gift of spirit been demonstrated by them, nor that the same acts beyond the powers of the elements, or accomplishes greater works than could the blood alone. As for us who use our senses to guide us in the scrutiny of things, nowhere have we been able to find anything of the kind. Furthermore, there exist no cavities destined for the generation or preservation of these spirits, or even assigned thereto by the persons aforesaid."[312] A little farther on we read:-- "I deem it, however, most wonderful that spirits which draw their origin from heaven and are adorned with such surpassing endowments should be nourished by our common and elemental air; especially seeing that their advocates hold that none of the elements can act beyond its own powers....[313] What need then is there, say I, of that foreign guest, ethereal heat, since all can be accomplished by the blood, even as by it; while from the blood the spirits cannot withdraw a hair's breadth without perishing? Most assuredly nowhere do they wander or penetrate as separate bodies without the blood. For whether it be said that they are generated, nourished, and increased from the thinner part of the blood, as some believe, or from the primitive moisture, as others hold; yet it is confessed that they are never found outside the blood but forever cleave to the same as to their sustenance, as flame does to oil or to a wick. Wherefore their tenuity, subtility, mobility, and so forth, confer no greater advantage than does the blood which they continually accompany. It follows that the blood suffices and is fit to be the immediate instrument of the soul, since the blood is present everywhere and most swiftly permeates hither and thither."[314]