502 ON GENERATION. 



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. 



