164 INTRODUCTION. 



what else, as we have it delivered to us by writers. In like 

 manner, before a fowl had attained to maturity or perfection, 

 because capable of engendering its like, it was a chicken ; 

 previous to which it was an embryo or foetus in the egg ; and 

 before this, Hieronymus Fabrieius, of Aquapendente, has ob- 

 served rudiments of the head, eyes, and spine. But when he 

 asserts that the bones are formed before the muscles, heart, 

 liver, lungs, and precordial parts, and contends that all the 

 internal organs must exist before the external ones, he follows 

 probabilities according to previous notions rather than inspec- 

 tion ; and quitting the evidences of sense that rest on anatomy, 

 he seeks refuge in reasonings upon mechanical principles; a 

 procedure that is anything but becoming in a great anatomist, 

 whose duty it was faithfully to narrate the changes he observed 

 taking place day by day in the egg, up to the period when the 

 foetus is perfected ; and this the rather as he expressly proposed 

 to himself to write the history of the formation of the chick in 

 the egg, and to exhibit in figures what happens in the course 

 of each successive day. It would have been in harmony with 

 such a design, I say, had we been informed, on the testimony 

 of the senses, of what parts are formed first, together, or sub- 

 sequently in the egg; and not had mere opinions or musty 

 conjectures, and the instances of houses and ships, adduced in 

 illustration of the order and mode of formation of the parts. 



We, therefore, in conformity with the method proposed, shall 

 show in the first place in the egg, and then in the conceptions 

 of other animals, what parts are first, and what are sub- 

 sequently formed by the great God of Nature with inimitable 

 providence and intelligence, and most admirable order. Next 

 we shall inquire into the primary matter out of which, and the 

 efficient cause by which generation is accomplished, and also 

 the order and economy of generation, as observed by us ; that 

 from thence, from its own work, we may have some certain in- 

 formation of the several faculties of the formative and vege- 



