SECT. 3] AND EIGHTEENTH CENTURIES 157 



an entirely new phase in embryology. Together with Rene Descartes' 

 treatise on the formation of the foetus, Gassendi's De generatione 

 animalium et de animatione foetus marks a quite different attitude to the 

 subject. Harvey had adopted a rather contemptuous position about 

 the "corpuscularian or mechanical philosophy", which was then 

 coming in, and had expected even less help from it in the solution 

 of his problems than from his equally despised "chymists". Gassendi 

 now set out to show that the formation of the foetus could be explained 

 on an atomistic basis: and, using the Galenic physiology and the 

 new anatomy as a framework, he set forth his theory in full. As we 

 read it through at the present day, however, we cannot avoid the 

 confession that it was not a success. In spite of his frequent 

 quotations from Lucretius and his persuasive style, it does not 

 carry conviction. The truth of the matter was that the time was 

 not ripe for so great a simplification. The facts were insufficiently 

 known, and that Gassendi is not quite as interested in them as he is 

 in his theory is shown by the circumstance that he only mentions 

 Harvey once. 



Gassendi examines in turn the Aristotelian and the Epicurean 

 doctrines of embryogeny and rejects them both, the former on the 

 ground that the change from tgg to hen is too great and difficult 

 for anything so shadowy and ghost-like as a "form" to accomplish, 

 and the latter because it leaves no room for teleology. He therefore 

 adopts as the basis of his system atomism + preformationism, al- 

 leging that all the germs of living things were made at the creation, 

 but that they come to their perfection as atomic congregations in an 

 atomistic universe. Thomas' monograph is a valuable help to the 

 study of this very interesting thinker. 



At exactly the same time, Descartes was speculating on the same 

 subject. Added to his posthumous De Homine Liber (1662) is a treatise 

 on the formation of the foetus. He may also have written a work 

 On the generation of animals, for a manuscript with that title was found 

 among his papers after his death, and was believed to be in his 

 handwriting. There is evidence, however, that it is not his, and though 

 it was published in Cousin's edition of his works, we may safely 

 neglect it, agreeing, in the words of that editor, that it is "a fragment 

 in which very mediocre and often quite false ideas struggle to light 

 through the medium of a style devoid alike of clarity and of grandeur ". 

 It must be admitted, however, that even his main treatise is very 



