selves upon the use of these terms without, as I apprehend, rightly understanding their meaning. There is, in fact, no occasion for searching after spirits foreign to, or distinct from, the blood; to evoke heat from another source; to bring gods upon the scene, and to encumber philosophy with any fanciful conceits ; what we are wont to derive from the stars is in truth produced at home : the blood is the only calidum in- natum, or first engendered animal heat ; a fact which so clearly appears from our observations on animal reproduction, particu- larly of the chick from the egg, that it seems superfluous to multiply illustrations.
There is, indeed, nothing in the animal body older or more excellent than the blood; nor are the spirits which are dis- tinguished from the blood at any time found distinct from it; for the blood without heat or spirit is no longer blood, but cruor or gore. "The blood," says Aristotle, 1 "is hot in a certain manner, in that, namely, in virtue of which it exists as blood, just as we speak of hot-water under a single term ; as subject, however, and in itself finally, blood is blood, it is not hot : so that as blood is in a certain way hot per se, so is it also in a certain way not hot per se : heat is in its essence or nature, in the same way as whiteness is in the essence of a white man; but where blood is by affection or passion, it is not hot per se."
We physicians at this time designate that as spirit which Hippocrates called impetum faciens, or moving power; im- plying by this whatever attempts aught by its own proper effort, and causes motion with rapidity and force, or induces action of any kind ; in this sense we are accustomed to speak of spirit of wine, spirit of vitriol, &c. And therefore it is that physicians admit as many spirits as there are principal parts or operations of the body, viz. animal, vital, natural, visual, audi- tory, concoctive, generative, implanted, influent, &c. &c. But the blood is the first produced and most principal part of the body, endowed with each and all of these virtues, possessed of powers of action beyond all the rest, and therefore, /car' co- yrrlv in virtue of its pre-eminence, meriting the title of spirit.
Scaliger, Fernelius, and others, giving less regard to the
1 De Part. Anim. lib. ii, cap. 3.
