Harvey was among the first to disbelieve the erroneous doctrine of the “preformation” of the fetus; he maintained that the organism derives from the ovum by the gradual building up and aggregation of its parts.  The chapter on on labor (“De partu”) in this book is the first work on that subject to be written by an Englishman, and the first original work on obstetrics by an English author. This book also demonstrates Harvey’s intimate knowledge of the existing literature on the embryology. He corrected many of the errors of Fabricius. Harvey considered this to be the culminating work of his life, and more significant than De motu cordis. See The analysis of the Degeneratione animalium of William Harvey by A. W. Meyer, Stanford Univ. Press, 1936. First English translation, London, 1653. New translation, with introduction and notes by G. Whitteridge, Oxford, Blackwell, 1980.