text. I could have characterized the table best by 

 saying that with the exception of the earliest period 

 of life of the embryo, which was not presented there, 

 the table was richer in its content than all that was 

 published earlier concerning this question. The later 

 series of engravings by the Englishman Ham do not give 

 one-fourth the clarity presented by this outlined 

 drawing. It is as if the author wanted to be provocative, 

 using line drawings and leaving to posterity the question 

 of who he was and where he had gone. It is necessary to 

 remember that he wrote in 1808, for four years after 

 which not a single significant work on the development 

 of the chicken appeared. He was considered the principal 

 founder of a new series of investigations. Being the 

 first in this respect, he had no guide, because there 

 were none who could have assumed this leadership. 10 



It will be useful to give a brief statement of those 

 sections of the dissertation in which are described those more 

 or less complete observations and the wonderfully specific 

 drawings. These observations concern the paunch (cicatrice), 

 the albumin ligaments, the development of the jaws and beak 

 with its hillock, the yolk-intestinal duct, the digestive 

 tract, and the extremities. Below are given Tredern' s data, 

 references, and comments in the form of notes at the end of 

 the book. 



THE PAUNCH, OR CICATRICE, was called by the old 

 embryologists the cock's trace or cover. It later received 

 the name embryonic layer or embryonic disk. Tredern only 

 mentioned that he could observe this formation on the surface 

 of the egg yolk while they were still in the ovary, something 

 that none of his predecessors had succeeded in doing 

 CFigure 18, 1). 



10. The stated opinion of Baer was taken from two of his 

 articles about Tredern, in DAS INLAND (April 7, 

 1836) and in BULL. ACAD. SCI. ST. PETERSBURG, 

 19 (1874) . 



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