ON GENERATION. 381 



aught as yet been urged against it by any one which has seemed 

 greatly to require an answer. Wherefore I imagine that I 

 shall perform a task not less new and useful than agreeable to 

 philosophers and medical men, if I here briefly discourse of the 

 causes and uses of the circulation, and expose other obscure 

 matters respecting the blood ; if I show, for instance, how much 

 it concerns our welfare that by a wholesome and regulated 

 diet we keep our blood pure and sweet. When I have accom- 

 plished this it will no longer, I trust, seem so improbable and 

 absurd to any one as it did to Aristotle 1 in former times, that 

 the blood should be viewed as the familiar divinity, as the soul 

 itself of the body, which was the opinion of Critias and others, 

 who maintained that the prime faculty of the living principle 

 (anima) was to feel, and that this faculty inhered in the body 

 in virtue of the nature of the blood. Thales, Diogenes, Hera- 

 clitus, Alcmseon, and others, held the blood to be the soul, 

 because, by its nature, it had a faculty of motion. 



Now that both sense and motion are in the blood is ob- 

 vious from many indications, although Aristotle 2 denies the 

 fact. And, indeed, when we see him, yielding to the force of 

 truth, brought to admit that there is a vital principle even 

 in the hypenemic egg; and in the spermatic fluid and blood 

 a " certain divine something corresponding with the element of 

 the stars," and that it is vicarious of the Almighty Creator ; and 

 if the moderns be correct in their views when they say that the 

 seminal fluid of animals emitted in coitu is alive, wherefore 

 should we not, with like reason, affirm that there is a vital prin- 

 ciple in the blood, and that when this is first ingested and 

 nourished and moved, the vital spark is first struck and en- 

 kindled ? Unquestionably the blood is that in which the vege- 

 tative and sensitive operations first proclaim themselves ; that 

 in which heat, the primary and immediate instrument of life, 

 is innate ; that which is the common bond between soul and 

 body, and the vehicle by which life is conveyed into every 

 particle of the organized being. 



Besides, if it be matter of such difficulty to understand the 

 spermatic fluid as we have found it, to fathom how through it 

 the formation of the body is made to begin and proceed with 



1 De Anima, lib. i, cap. 2. 



2 De Hist. Anim. lib. i, cap. 19 ; et de Part. Anim. lib. ii, cap. 3. 



