THE STRUCTURE OF THE HUMAN SKULL. 121 



depression Cor the optic commissure, there is a transverse ridge, 

 the iuberculum selhe* The region between the synchondrosis 

 and the tuberculum is the upper surface of the basi-sphenoid. 

 Its under-surface (Fig. 53) exhibits a median, wedge-shaped 



portion, terminating abruptly at the point e, on each side of 

 which are stuck on, as it were, two delicate bones, shaped 

 somewhat like sugar-bags, with their wide and open ends 

 directed forwards and their apices backwards. These are the 

 bones of Berlin, or cornua sphenoidalia, which do not properly 

 belong to the basi-sphenoid, but coalesce with it in the course of 

 growth. 



From the tuberculum sellw (c) to the point (b) in the upper 

 view (Fig. 52), and from the point e, to b of the lower view 

 (Fig. 53), the middle region of the cranio-facial axis belongs 

 to a third bone, the presphenoid (PS) which terminates the 

 basi-cranial axis. 



I say terminates the basi-cranial axis, because the appear- 

 ance of a continuation forwards of that axis by the crista galli, 

 or upper margin of the lamina perpendicular is of the ethmoid 

 (see Fig. 50), is altogether fallacious, depending, as it does, upon 

 a special peculiarity of the highest Mammalian skulls, which 

 arises from the vast development of the cerebral hemispheres. 

 In the great majority of Mammalia below the Apes, in fact, the 

 free edge of the lamina perpendicular is is not horizontal, but 

 greatly inclined, or even vertical ; and in these cases the whole 

 lamina plainly appears to be, what it really always is, beyond, 

 or anterior to, the floor of the brain-case ; while the true basi- 

 cranial bones are parts of the floor of the brain-case. 



During foetal life, the basi-sphenoid and presphenoid are 

 united only by synchondrosis, traces ol which may even be 

 discovered (as Virchow has shown) as late as the thirteenth 

 year, or later. Even before birth the two bones become 

 anchylosed superiorly, their junction being marked by the 

 tuberculum sellse ; and the remains of the synchondrosis extend 



* Where tie terms employed in our ordinary handbooks of Human Anatomy 

 do not suffice for my purpose, I adopt those used by Henle in his classical 

 "Handbuch der Systematischen Anatomic des Menschen," a work of great ac- 

 curacy and comprehensiveness, now in course of publication. 



