ioo POPULAR SCIENCE MONTHLY. 



Harvey, little of substantial value had been produced. The earliest 

 attempts were vague and uncritical, and, naturally, embraced only 

 fragmentary views of the more obvious features of body formation. 

 Nor, indeed, are we to look for much advance in the field of embry- 

 ology even in Harvey's time. The reason for this will be obvious 

 when we remember that the renewal of independent observation had 

 just been brought about in the preceding century, when, in 1543, the 

 science of anatomy had been reformed by Vesalius. 



Harvey himself was one of the pioneers in the intellectual awaken- 

 ing. By his immortal discovery of circulation of the blood (1619- 

 1628) he had established a new physiology. Now, studies on the 

 development of the body are more special, they involve observations 

 on minute structures and recondite processes, and must, therefore, 

 depend upon considerable advances in anatomy and physiology. 

 Naturally the science of embryology came later. 



Harvey. — Harvey's was the first attempt to make a critical analysis 

 of the process of development, and that he did not attain more was 

 not due to limitations of his powers of discernment, but to the 

 necessity of building on the general level of the science of his time, 

 and, further, to his lack of instruments of observation and technique. 

 Nevertheless, Harvey may be considered as having made the first in- 

 dependent advance in embryology. 



By clearly teaching, on the basis of his own observations, the 

 gradual formation of the body by aggregation of its parts, he an- 

 ticipated Wolff. This doctrine came to be known under the title of 

 ' epigenesis,' but Harvey's epigenesis* was not, as Wolff's was, directed 

 against a theory of predelineation of the parts of the embryo, but 

 against the ideas of the medical men of the time regarding the 

 metamorphosis of germinal elements. It lacked, therefore, the 

 dramatic setting which surrounded the work of Wolff in the next cen- 

 tury. Had the doctrine of preformation been current in Harvey's 

 time, we are quite justified in assuming that he would have assailed 

 it as vigorously as Wolff did. 



Harvey's embryological work was published in 1651 under the 

 title ' Exercitationes de Generatione Animalium.' It embraces not 

 only observations on the development of the chick, but also on the 

 deer and some other mammals. He being the court physician of Charles 

 I., that sovereign had many deer killed in the park, at intervals, in 

 order to give Harvey the opportunity to study their development. 



As fruits of his observation on the chick, he showed the position f 

 in which the embryo arises within the egg. viz., in the white opaque 



* As Whitman has pointed cmt, Aristotle taught epigenesis as clearly as 

 Harvey and is, therefore, to be regarded as the founder of that conception. 



t Fabricius supposed that the chick developed from the twisted cords of 

 the white of the egg. 



