SKULL OF A 43-MM. HUMAN FETUS. 



77 



missure, forms the lingula. Lewis (1920) thinks 

 it probable that the alar process is largely incor- 

 porated into the body of the mature bone and 

 brings forward several lines of evidence favoring 

 this view, including the relations of the carotid 

 artery and the nerve of the pterygoid canal to the 

 process, and also some interesting craniometric 

 findings. He agrees in the general view that the 

 alar process also forms the lingula, but does not 

 mention the alicochlear commissure or alicoch- 

 lear process. 



ALICOCHLEAR COMMISSURE. 



The alicochlear commissure is 20 micra in length 

 and conical in form, The lateral diameter of its 

 base is slightly greater than the dorso-ventral. 

 With the projecting cochlear pole it forms the 

 lateral border of the carotid foramen. Jacoby 

 found it in the 30 mm. stage, but Levi did not 

 describe it. Fawcett (1910a, p. 216) found that 

 in a 30-mm. embryo "the processus alaris sends 

 backwards a pointed process which comes into 

 contact with the auditory capsule." He added 

 that "this condition is even visible in the 110 mm. 

 stage." It is not clear whether there were actual 

 cartilaginous unions with the otic capsule. 

 Kernan found, in the 20 mm. stage, an alicochlear 

 process which came into contact with the cochlea 

 but did not unite with it. He considers it to be 

 only temporary in man. In the corresponding 

 region of la there was a projection backward 

 toward the cochlea, but no actual cartilaginous 

 union. 



CAROTID FORAMEN. 



The carotid foramen is irregularly rounded in 

 outline (figs. 1, 2) with a narrow lateral diverti- 

 culum between the alicochlear commissure and 

 the cranial border of the cochlea. Views of its 

 medial and lateral walls, which have been de- 

 scribed, are seen in figures 10 and 15 respectively. 

 The internal carotid artery occupies only this 

 outer angle. It passes in an oblique direction 

 from below upward, forward, and slightly inward, 

 close to the alicochlear commissure, to overlie the 

 alar process in the region of the future cavernous 

 sinus. Its course beneath the otic capsule has 

 already been noted. There is no indication of the 

 canal through which the artery later passes in the 

 osseus skull and it is evident that the future devel- 

 opment of the region at the cranial end of the 

 cochlea must be characterized by considerable 

 extension, there being developed between the 

 carotid foramen and the membranous cochlea a 

 lengthy piece of bone. In the mature skull, too, 



the carotid foramen is merely the inner end of the 

 foramen lacerum, since the backwardly projecting 

 lingula does not reach to the petrous portion of the 

 temporal bone, as a rule. 



TEMPORAL WING. 



The connection of the temporal wing with the 

 alar process does not take place directly from the 

 outer extremity of the latter, but rather from an 

 ' area at the outer end of its ventral surface. This 

 is somewhat triangular (fig. 16) with the apex 

 directed forward and inward, and is gently convex. 

 It is directed downward, forward, and slightly out- 

 ward. The reverse side, upon the dorsal surface 

 of the wing, appears in figures 26 and 27, its inner 

 boundary being separated from the adjoining 

 surface by a low ridge. In the sections where this 

 division has been made, a very thin strip of young 

 cartilage may be seen, which separates the two 

 portions of the wing. 



If the alar process and wing be looked at from 

 below, there is seen a sharp notch where they 

 join, but when the separation of the parts is 

 effected as outlined above it is evident that this 

 notch belongs to the alar process. In it is the 

 nerve of the pterygoid canal, lying just above and 

 a little medial to the caudo-medial angle of the 

 wing (fig. 26) . It is in this region that the future 

 pterygoid canal will be formed. This notch is 

 continued around upon the caudal aspect of the 

 wing, and may be seen from the side, as in figure 

 6, between the lateral extremity of the processus 

 alaris (above), and the caudo-medial angle of the 

 ala (below). 



The temporal wing, resembling that of la 

 quite closely, is a rhomboidal block of cartilage 

 which lies with its long axis directed forward, 

 outward, and upward. It hangs altogether below 

 the level of the alar process. Perforating the 

 block from above, downward, and forward, is 

 the conspicuous foramen rotundum (figs. 2, 26, 

 27), situated nearer the medial than the lateral 

 border and nearer the anterior than the posterior 

 end. The antero-lateral salient portion may be 

 recognized as the ascending lamina, while the 

 pterygoid process projects farthest ventrally and 

 is just lateral to the medial pterygoid plate 

 (fig. 29). The two surfaces may be described 

 as dorsal and ventral, though they look a little 

 posteriorly and anteriorly respectively. The 

 dorsal surface (fig. 1) is somewhat convex from 

 side to side and from before backward, and pre- 

 sents a sharp upward edge of young cartilage 

 which borders the foramen rotundum laterally. 

 In front of the foramen there is a narrow and 



