78 



SKULL OF A 43-MM. HUMAN FETUS. 



shallow transverse concavity, while medial to the 

 foramen is a narrow isthmus of young cartilage 

 which joins the thicker anterior and posterior 

 parts (figs. 11, 26, 27). This isthmus is by far the 

 most slender part of the wing and seems to be the 

 last part of the foraminal border to chondrify; 

 for in earlier stages the foramen is incomplete 

 here, the greater wing appearing as a hook with its 

 tip stretching medially, forming the notch which 

 represents the foramen (Lewis et al.). In la it 

 was stouter, though still of comparatively young 

 cartilage. Behind the foramen is the stoutest 

 portion of the wing. Its upper surface slopes 

 downward and backward, its medial region, under- 

 lying the alicochlear commissure, presenting a 

 low ridge, directed principally backward, which 

 is edged with young cartilage. This ridge ter- 

 minates caudally in the caudo-medial angle of the 

 wing, some distance above the level of the ptery- 

 goid process. 



The ventral surface, which also looks forward 

 and inward (figs. 2, 3), shows the rounded lateral 

 and superior portions of the foraminal border. 

 The slender medial border is also seen. Just 

 below the foramen is a rounded forward projec- 

 tion from the pterygoid process, which passes 

 backward to be lost at the caudo-lateral angle of 

 the mass. A shallow groove is medial to this 

 ridge. It extends from the foramen to the caudal 

 edge of the wing. Medial to this is a rounded 

 area which curves upward to the mesial border. 



The anterior boundary is quite sharply marked ; 

 the lateral is distinct in front, becomes blunt and 

 rounded behind, and shows a shallow outward 

 concavity. The posterior is best marked me- 

 dially, where is terminates in the blunt point 

 already mentioned. The medial border is thin 

 in front (figs. 11, 27); from the slender foraminal 

 portion of this the boundary is continuous, me- 

 dially, with the thin cranial edge of the processus 

 alaris (fig. 11), there being here a narrow edging of 

 young cartilage. The caudal portion of the 

 medial boundary of the wing is lost in the con- 

 nection with the alar process, except posteriorly, 

 where it runs over upon the caudo-medial angle. 



Evidences of beginning ossification. — Particularly 

 in the region of the pterygoid process, and lateral 

 to and below the foramen rotundum (see Fawcett, 

 1910a, fig. 13), but extending out from this, 

 especially forward, the cartilage shows evidence of 

 preparation for ossification (figs. 11,26, 27, and 29). 

 It involves practically the entire outer half of the 

 wing and extends inward to about the middle of 

 the mass lying in front of the foramen rotundum. 

 The cranial half, however, is not so strongly 



marked as the caudal and, as has been noted, 

 the upper edge of the lateral margin of the fora- 

 men is edged with precartilage. Below this ridge 

 the lateral wall of the foramen shows preossifica- 

 tion changes. 



The semilunar ganglion lies above the greater 

 wing, though separated therefrom by an interval 

 equal to its own thickness. Its posterior third is 

 applied quite closely to the antero-Iateral aspect of 

 the cochlea (figs. 15, 16). Its root and branches 

 are all well seen in these figures. The root pierces 

 the dura just above the level of the ganglion. 

 The ophthalmic division, much the smallest, 

 passes forward through the wide superior orbital 

 fissure, seen in figure 1. The maxillary division 

 traverses the foramen rotundum (figs. 26, 27, 29) 

 and gives off its sphenopalatine branches and 

 twigs to the sphenopalatine ganglion (fig. 27), 

 while the remainder of the fibers pass downward 

 and forward as the infraorbital nerve. The man- 

 dibular division courses downward and a little 

 outward and backward, as seen in figure 16. As 

 yet there is no foramen ovale. 



In figure 16 the course of the great superficial 

 petrosal nerve may be followed as it passes for- 

 ward close to the outer surface of the cochlea just 

 behind the mass of the semilunar ganglion. At 

 the cranial end of the cochlea it comes to underlie 

 the alicochlear commissure and the internal carotid 

 artery. It then turns more directly forward, 

 diverging from the artery, which is now separated 

 from it by the alar process. In making this turn 

 it passes above the caudomedial angle of the tem- 

 poral wing (figs. 26 and 27) and comes, as the nerve 

 of the pterygoid canal, to occupy the notch between 

 the process and the wing proper. Traced forward 

 from this, it is seen entering the sphenopalatine 

 ganglion, as the figures show. 



The medial pterygoid plate (figs. 26, 29) is a thin 

 strip of membrane bone which is directly con- 

 tinuous below and behind with the rounded para- 

 sphenoidal cartilage, representing the hamulus. 

 The bone and cartilage form a right angle (figs. 

 26, 28). The hamulus alone is seen in figures 2, 

 3, and 6. The cartilage and bone seem to be 

 quite intimately joined together, and there is no 

 definite boundary between them — in fact, the 

 appearance of the cartilage suggests that it is in 

 process of calcification preparatory to ossification. 

 The lower end of the anterior border of the plate 

 resembles cartilage. In the description of 7a 

 it was noted that this cartilage differs in histologi- 

 cal appearance from that of the chondrocranium 

 proper. The pointed upper end of the bony plate 

 lies but a short distance below the caudomedial 



