‘Let us then blush in this so ample and so wonderful field of nature to credit other mens traditions only, and thence coine uncertain problemes, to spin out thorney and captious questions. Nature her selfe must be our adviser; the path she chalks out must be our walk: for so while we confer with our own eies, and take our rise from meaner things to higher, we shall be at length received into her Closet-secrets.’ (William Harvey, Anatomical Exercitations (London, 1653), a6b.)

BIBLIOGRAPHICAL PREFACE

HARVEY had for a great number of years experimented and recorded his observations on the development of the chick embryo and of other animals. There are many references to the subject in his writings on the heart and circulation of the blood, and he even mentions in his second essay to Riolan matters ‘which I will take notice of in the generation of creatures’, so that his book, De Generatione Animalium, had certainly taken shape at that date (1649). It is evident from references in the sixth Exercise of this work that this interest in the subject of generation had been initiated by his association with the great Fabricius when he was at Padua, 1598—1602. He may even have assisted in the experiments described by Fabricius, whose book De formato fetu, was published in 1600. Although the book had been so long in gestation he was reluctant to publish it, and it was only owing to the importunity of his friend, Dr (afterwards Sir) George Ent, that he eventually in 1651 allowed it to be printed. It may be surmised that his reluctance was due partly to the weariness of his age and infirmities, for Ent gained his point by undertaking to see the book through the press, so that the burden and difficulty of deciphering his own crabbed writing was removed from the author's shoulders. Ent reports in his dedication the conversation with Harvey in which he secured his consent to publication, and remarks at the end that ‘as our author writes a hand which no one without practice can easily read, I have taken some pains to prevent the printer committing any very grave blunders through this, a point which I observe not to have been sufficiently attended to in the small work of his which lately appeared [no doubt De Circulatione Sanguinis, 1649]’.