FIGURE 4 



Section of 20 inm. human embryo, nearly parallel to Isasal plate. 



1, Slender area of basal plate 



2, Blastemal anlage of ligamentiim 



dentis epistrophei 



3, Costal bar of lamina alaris 



4, Transverse and costal process, 



occipital vertebra 



5, Cranio-mesial extension of costa 



bar 



6, Perichondrial layer separating cos- 



tal bar and transverse process of 

 occipital vertebra 



7, Ala hypochiasmatica 



8, Ala temporalis, processus alaris 



9, Ala temporalis, processus ascen- 



dens 

 10, Foramen rotundum 

 //, Foramen ovale 



12, Processus alicochlearis 



13, Chorda dorsalis 



14, Hypophyseal stalk 



15, Malleus 



16, Incus 



17, Stapes 



18, Reichert's cartilage 



19, Interhyale 



20, Arteria carotis 



21, Foramen perilymphaticu:ii 



634 



