3:iS TTTRo'l'A : OX TTTE 8E170- AMNIOTIC CONXECTTOX. 



reo'ard to some fundamentnl points in the structure and relations of 

 tlie foetal memhranes of the chick. It is generally assumed hy writers 

 on eml)ryol<^n'v that several amniotic f(^lds, I'ising over the emhrvo. 

 come togethei' in the median line aho\ e the emhryo. t]\v edges of which 

 entirely coalesce and whose cavities hecome continuous from one side 

 to the other. The classical scries of diagrams given in Foster and 

 ]>alfour's Elements of Embryology (2nd ed., pp. 28-3.')). and copied 

 very extensively, is constructed on this supposition. Some authors, as 

 Schenk,' Köliiker, and Hertwig, have, it is true, remarked that the 

 cavities of tlie lateral folds are separated hy a longitudinal partition 

 (n;nned ' Amiiionnaht ' by Köliiker) for some time after tlie amniotic 

 cavity is closed ; luit they also state that shortly afterwards, the parti- 

 tion breaks down, so that the cavities of the former lateral folds 

 l)ecome dh'ectly continuous and the amnion proper entirely isolated 

 fr(3m the serous envelope. In reality the facts are very different. 

 While the horse-shoe shaped anterior amniotic fold grows backwards 

 over the dorsal surface of the embryo, the cavities of the lateral folds are 

 not in coalescence in the median line, l)ut ai-e from the first separated 

 from each other by a ]>artition which never breaks down. This 

 is quite similar to the state of things in Chelonia, recently described 

 by Mitsukuri,"^ who gave the name of '' Sero-Amniotic Connection" 

 to this partition. This sero-amniotic connection undergoes in the 

 cluck some histological changes in the course of the development of 

 the embryo, but remains as a partition to the last day of the incuba- 

 tion. This persistence of the sero-amniotic connection exercises, as in 

 Chelonia, a great and complex influence on the foetal membranes in 

 later stages. At the suggestion of IVofs. Mitsukuri and Ijima, 1 have 



1. S. L. Schenk: Beiträg,-e zur Lehre von Amnion. Arch. i. Mikros. Anat. Bd. 7. 1871. 



2. K. Mitsukuri: On the Poetal Meuiliranes of Chelonia. .Tourn. of the Colleo-e of Science, 

 I nil., l^niv., Ja]ian. Vol. IV., Pt. 1. 1890. 



