40 



LECTURE II. 



every cliange in the development and juncture of ttese tliree 

 fundamental bones must necessarily influence both parts of the 



Fig. 6. Side view of the skuU, as in preceding figure, a. to m. have the 



same signification. 



n. Squama of temporal bone. o. Mastoid process, p. External auditory 

 aperture. q. Temporal ridge, r. Zygomatic arch. s. Wing of the sphe- 

 noid bone. t. Zygoma (cheek bones). u. Upper jaw. v. Nasal spine. 

 w. Orbit. X. Nasal bone. y. Nasal suture, z. Glabella. 



head^ inasmuch as these in a certain degree represent the two 

 arms of a lever which finds its central point in these bones. 

 On inspecting a skull sawn through^ so as to divide these 

 bones longitudinally through the centre, we perceive that they 

 do not, at aU events, in normal skulls, present a straight 

 line, but an angular surface, the centre of which is in a depres- 

 sion of the sphenoid bone called the "Turkish saddle" (sella 

 turcica). Upon this "saddle" rests an appendage of the 

 brain situated almost in the centre of the lower surface of the 

 cerebral mass. In the same spot where the angle is formed, 

 that peculiar cartilaginous body the chorda, terminates what 

 served as the central point for the formation of the vertebrae 

 of the embryo at the earhest period. It has been observed that 



