EXPERIMENTAL CHICK EMBRYOLOGY 



i;l+l 



Rudnick, on the other hand, hy isolation culture methods on plasma clots, found that 

 two primary germ layers the ectoderm and endoderm seem to function more-or-less indepen- 

 dently, and that the notochord and axial mesodermal structures apparently depend on the 

 deginltive organization of the streak and node, or the head process, for realization in 

 vitro. Below is presented a figure from her paper showing the recognizable differentia- 

 tions from various regions of the early blastoderm when explanted in vitro. 



MED PLATE SS'C 

 SENS EP 

 BOOmALL 

 MESENCHYME 

 ERYTH 50% 



[MED PL ATE J 

 HEART ? 

 MESENCnrME 

 ERYTH. 100% 



SENS EP 

 CHORDA ? 

 BODY WALL 

 MESENCHYME 

 ERYTH SO'/, 



MEDPLATE aS% 

 SENS- EP 

 BODY WALL 

 MESENCHYME 

 ERYTH .' 



MED PLATE 

 HEART 



HEART soil, 

 ERYTH 100% 



MED PLATE SOV . 



MESENCHYME 

 CHORDA' 

 HEART' 

 ERYTH 13 % 



\ HE ART SO '/. 



Operating diagrams, showing structures differen- 

 tiating from each piece. Approxlnrnte percentages 

 are given In cases where they are thought of 

 significance. 



From Rudnick I958: Jour. Exp. Zool. 75:599. 



THE METHOD OF CHOR lO-ALLANTOIC GRAFTING 



The grafting of early chick embryo parts to the chorio-allantois of an older (8^ to 

 10 day incubated) embryo has long since been perfected ( Headley, 192^, Willier, I92U) , 

 The highly vascularized chorio-allantois of the avian embryo is located close to the shell 

 membrane of an 8-day embryo, so that the shell 

 over it can be removed and the explant can be 

 placed upon it as a substrate for nutrition 

 and growth. If the shell is replaced and 

 sealed into place with melted paraffin, the 

 explant will generally become vascularized and 



will develop for 9 to 10 days and may be re- ^^ ^^ ^^^^ ^^ 

 covered before the natural breakdown of the ^^K ^^^^S^^^r ^^^ 

 extra-embryonic membranes on the 19th day of ^^B. ^^Hitf^lr / fj/ 

 incubation. 



Since there is complete isolation of the 

 explant, there are no persistent inductive 

 influences. However, the explant does come 

 under the hormonal and other influences ema- 

 nating from the blood of the host, and these 

 must be considered. Further, there is a 

 space limitation (within the host environment) 



Chick egg with window above the develop- 

 ing embryo. Black washer Is sealed to 

 the egg shell and to tlie covering cover- 

 glass with paraffin. Irregular margin of 

 torn shell membrane visible through the 

 window. Embryo can develop and hatch. 



