SECT-ION OF THE MASTODON HEAD. 119 



The cells are of various forms and sizes ; they are generally oblong, and Form, size, 



and 



from half an inch to three inches in length ; the diameter of the largest is communi- 

 cations 

 nearly an inch. These cells appear to communicate with the nasal cavity. fCeiis. 



There is one opening, quite, at the anterior part, where the anterior cells 



terminate. The posterior cells open into a large canal, under the vertex ; 



the partitions of the cells vary much in thickness, being thickest where 



they are connected with the tables of the cranium, and thinnest' at the 



edges of their openings of communication. The cells which correspond with 



the inferior occipital region, where there is a great mass of flesh covering 



the bone, are very few in number. Those about the Sella Turcica are quite 



numerous, and open into the back part of the nasal cavity ; one of these is 



very large, representing the sphenoidal sinus. 



Cerebral Cavity. — The cavity of the cranium is flattened from above cerebral 



Cavity. 



downwards, so as to give its transverse diameter a greater extent than 

 that from before backwards ; its transverse measurement being twelve 

 inches, while its greatest in the other direction is nine inches : its greatest 

 depth from above downwards is five inches. The superior surface of this 

 cavity is regularly vaulted ; the inferior is irregular, presenting three 

 different surfaces. The anterior or orbitar surface does not reach the 

 orbitar fossa ; the middle surface, or petrosal division, has a deep excavation 

 for lodging the middle lobes of the cerebrum ; the posterior division is 

 principally formed by the petrosal part of the os temporis in front, and 

 gives support to the lobes of the cerebellum. In the middle of this inferior 

 region we notice the projection of the Sella Turcica, with a slight excava- 

 tion on the superior surface, but no appearance of clinoid processes. Below 

 it are the diploic cells ; in front, the cribriform plate of the os ethmoides ; 

 posteriorly, the openings for the nerves, of which the foramen ovale is most 



