CHONDROCRANIUM OF A 20 MM. HUMAN EMBRYO 623 



The alae teiiiporales (figs. 1 and 3) are caudo- ventral to the 

 alae orbitales. In them two parts are distinguished, mesial and 

 lateral (Fiichs '10) (figs. 4, 5, 6). The mesial part, eranially 

 is known as the processus alaris. It is a short bar of cartilage 

 which arises from the ventro-cranial edge of the sphenoid body 

 and extends caudo-laterad. From the point of origin of the 

 lateral part of the temporal wing it continues caudally as the 

 processus ali-cochlearis to the cochlea, with which it comes in 

 contact, but does not unite. This whole process was described 

 by Jacoby as a cartilaginous bridge from the sphenoid to cochlea, 

 from the outer edge of which arose the outer part of the ala tem- 

 poralis or lamina ascendens. Levi found no trace of it in his 

 models. Macklin described it as approaching the cochlea, but 

 not very closely. 



In the region where it might be expected to join the cochlea, 

 he found a separate nodule of cartilage which he called the supra- 

 cochlear cartilage. The dorsal division, the commissura ali- 

 cochlearis, is not seen in Hert wig's models. It would appear to 

 be only a temporary structure in man, though found in many 

 mammals (DeBurlet, Olmstead Tl, Voit, Fischer). When pres- 

 ent, it bounds the carotid canal laterally. 



The lateral part of the ala temporalis (figs. 1, 4 and 6), or the 

 lamina ascendens, is a rhomboidal block of cartilage attached 

 by its mesial, dorsal corner to the processus alaris. Its ventral 

 edge is narrow; the dorsal edge is broadened into a flat surface 

 which the foramen rotundum perforates downward and forward 

 (fig. 6). The long axis of the structure points laterad. From 

 its caudal edge arise two processes of dense connective tissue 

 which embrace the third division of the fifth nerve, which is just 

 caudal to the ala temporalis. Thus is indicated the beginning 

 of the foramen ovale (fig. 4). 



There is no indication in the orbito-temporal region of any 

 remains of the primitive side wall mesial to the Gasserian gan- 

 glion and the structures contained in the cavum epiptericum and 

 cavum supra-cochleare (Voit), such as Voit found in the rabbit. 

 In his 40 mm. reconstruction, Macklin thought this primitive wall 

 might be indicated by the isolated nodule of cartilage at the 



