Figure 23. Pander's illustrations from "History of Development 

 of the Chicken in the Egg." 



A (I) Back side: bb — primary folds in their earliest condition; 

 q — fold of the fetal area above the primary folds. B{2) Back 

 side: bb — primary folds; at o they are arch-shaped, joined at 

 the future head end, and, conversely, separated at the tail 

 end. S(3) Back side: bb — primary folds; e — filament of the 

 spinal cord between the primary folds; d — knot- shaped end. 



(4) Primary folds closer, especially in the central part of 

 the fetus, where on both sides the first rudiments of the 

 spinal vertebrae are laid; below, where the thin filament of 

 the spinal cord terminates at e in a lancet shape, they again 

 disperse. (5) The peritoneal side: dd — end of the head 

 portion at which the lower edge of the heart is seen (k) ', 

 ef — spinal cord; h — intestinal folds, appearing as lateral 

 borders to the head portion; 11 — lateral borders of the head 

 portion; m — head. £"(6) Fetus from the side of the shell: 

 a — headj b — tail; c — spinal column, seen through the opening 

 of ,he amnion; d — same, under the amnion; e — opening of the 

 amnion. (7) Fetus from the side of the yolk: b — border of 

 the head portion; tail portion; d — intestinal folds; e — spinal 

 cord; ff — arterial stems; g — heart in form of twisted canal. 



(8) Fetus in the amnion: a — amnion; b — chorion sac; 

 d — place where all the veins enter the fetus; o — vessels of 

 the chorion; ee — descending veins; m — ascending vein; 

 / — upper arch of the heart; g — lower arch; h — bulb of aorta, 

 from which go out three arch- shaped curved arteries •t, uniting 

 in descending aorta k, Z — left artery with its lateral branch 

 n; o — vein, accompanying this branch. (9) aa — primary folds; 

 go — the cut place (see 10) . K (10) Transverse section 

 (see 9) : aa — primary folds; b — place where the spinal 

 column is situated. (11) aa — primary folds; bbb — head 

 portion; o — its lower border; g — its upper border; fff — borders 

 of the upper membrane of the head portion: dd — cut place 

 (see 12) . M (12) aa — primary folds; b — location of spinal 

 cord; oco — upper layer of the head portion; old intestinal 

 folds. H (13) aa — primary folds; b — place where the spinal 

 cord is formed; oo — folds of the internal layer of the head 

 portion, forming the heart; h — lower border of the head 

 portion; fff — border of the upper layer of the head portion; 

 d — tail portion; -ii, — place of the cut (see 14) . (14) 

 aa — primary folds; b — location of the spinal column; 



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