THE RISE OF EMBRYOLOGY 213 



Wolff's researches on the development of the intestines, 

 rescued the work from neglect and obscurity by publishing 

 a German translation of the same, and bringing it to the 

 attention of scholars. From that time onward Wolff's labor 

 was fruitful. 



His De Formatione Intestinonim rather than his Theoria 

 Generationis embodies his greatest contribution to embry- 

 ology. Not only is it a more fitting model of observation, but 

 in it he foreshadows the idea of germ-layers in the embryo, 

 which, under Pander and Yon Baer, became the fundamental 

 conception in structural embryology. Throughout his re- 

 searches both early and late, he likens the embryonic rudiments, 

 which precede the formation of organs, to leaflets. In his 

 work of 1768 he described in detail how the leaf-like layers 

 give rise to the systems of organs; showing that the nervous 

 system arises first from a leaf-like layer, and is followed, 

 successively, by a flesh layer, the vascular system, and lastly, 

 by the intestinal canal all arising from original leaf-like 

 layers. 



In these important generalizations, although they are 

 verbally incorrect, he reached the truth as nearly as it was 

 possible at the time, and laid the foundation of the germ- 

 layer theory. 



Wolff was a man of great power as an observer, and al- 

 though his influence was for a Ions; time retarded, he should 



O O ' 



be recognized as the foremost investigator in embryology 

 before Yon Baer. 



Few Biographical Facts.- -The little known of his life 

 is gained through his correspondence and a letter by his 

 amanuensis. Through personal neglect, and hostility to his 

 work, he could not secure a foothold in the universities of 

 Germany, and, in 1764, on the invitation of Catherine of 

 Russia, he went to the Academy of Sciences at St. Petersburg, 

 where he spent the last thirty years of his life. 



