HARVEY'S THEORY 25 



happens in art occasionally occurs in nature also; those 

 things, namely, take place by chance or accident which 

 otherwise are brought about by art, of this health (ac- 

 cording to Aristotle) is an illustration. And the thing 

 is not different as respects generation (in so far as it is 

 from seed) in certain animals; their semina are either 

 present by accident, or they proceed from an univocal 

 agent of the same kind. For even in fortuitous semina 

 there is an inherent motive principle of generation, which 

 procreates from itself and of itself; and this is the same 

 as that which is found in the semina of congenerative ani- 

 mals — a power, to wit, of forming a living creature." ^ 

 But at first he had said that those invisible seeds, like 

 atoms floating in the air, were scattered hither and 

 thither by the winds ; although he never explains whence 

 or from whom they take origin ; only it may be gathered 

 from the above quoted words that he believes that those 

 fortuitous seeds, flying in the air and carried by winds, 

 proceed from an agent not univocal, to express myself 

 in the language of the schools, but equivocal. Perhaps, 

 however, he would have stated his opinion with greater 

 clearness and precision if the notes which he had col- 

 lected on this subject had not been dispersed during the 

 tumult of civil war, to the deplorable loss of the republic 

 of philosophy. Many persons would have difficulty in 

 believing that Harvey could have hit upon the truth, 

 in as much as they obstinately assert that it is impossible 

 to indicate the efficient cause of the procreation of in- 

 sects. The subtlest philosopher of past centuries, after 

 vainly seeking it in our world, declared that the imme- 



1 Anatomical Exercises on the Generation of Animals (1651). 

 Translated by Robert Willis. Works of William Harvey. Lon- 

 don: Sydenham Society, 1847. p. 427. 



