THE RISE OF EMBRYOLOGY 213 
Wolff’s researches on the development of the intestincs, 
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 Intestinorwm rather than his Theoria 
Generalionis 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 Von Baer, became the fundamental 
conception in structural embryology. Throughout his re- 
searches both early and late, he likens the embryonicrudiments, 
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 long time retarded, he,should 
be recognized as the foremost investigator in embryology 
before Von 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. 
