322 CHARLES CLIFFORD MACKLIN 



by the reticular parietal bone (fig. 4). These structures enclose 

 the lower and posterior portion of the cranial cavity. 



The anterior mass is composed principally of the facial parts, 

 and contrasts with the posterior in being narrower from side to 

 side in its lower part, and in presenting a greater proportion of 

 osseous material. Its surface is also much more irregular and 

 uneven. In front of the pars canalicularis we see, in a recess 

 which lies ventro-lateral to the two parts of the otic capsule, an 

 irregular mass of cartilaginous and osseous structures, in which 

 we recognize the anlagen of the auditory ossicles and the upper 

 part of Meckel's cartilage, the latter appearing above the small 

 tympanic and goniale (fig. 2), and being covered laterally by 

 the squamo-temporalis. Below these structures, with its hook- 

 like proximal extremity lying in a small cavity, but unconnected 

 with the rest of the chondrocranium, is the slender shaft of Reich- 

 erf s cartilage. 



Above the otic capsule the large open space which will later 

 form the middle cranial fossa is again apparent, and through 

 this we see the lateral aspect of the hypophyseal fossa (fig. 3), 

 with the high dorsum sellae, upon which are the ventrally pro- 

 jecting posterior clinoid processes, hmiting it posteriorly. In 

 the anterior wall of the sella turcica is the middle clinoid process 

 (present on the right side only) and above this is to be seen the 

 orbital wing of the sphenoid, the gentle curvature of the latter 

 being broken by the anterior clinoid process, and its outer and 

 posterior extremity terminated by a sharp process, projecting dor- 

 sally. Below the ala orbitalis, and separated from it by the wide 

 and unclosed superior orbital fissure, is the ala temporahs, sup- 

 ported by a short processus alaris, the rounded extremity of the 

 latter almost touching the ventral pole of the cochlea, and being 

 quite close to the cartilago supracochlearis, which is plainly 

 visible from the side. 



Looking at the skull from a more anterior position we see, 

 above, the cavity of the orbit, roofed over by the cartilage of 

 the orbital wing of the sphenoid, and by the orbital portion of 

 the frontal bone (fig. 4) ; limited medially by the shelving posterior 

 portion of the ectethmoid; but widely open downwards and out- 



