in.] THE CRANIAL SKELETON. 105 



process is remarkable, and bears relation to the absence of 

 an erect posture of the body a posture which distinguishes 

 man from the other members of his order. 



Air-cells which exist, even in man, in the mastoid, extend 

 into the substance of the squamous element in the Gorilla, 

 and sometimes, as in Macroscelides and Pedetes, the mastoidal 

 air cavities are enormous, causing great projections of the 

 skull. 



A large vaginal process is peculiar to man, that part being 

 represented but slightly even in the Gorilla. 



The carotid canal is far from being a constant character of 

 the temporal bone, even in Mammals. Often, as e.g. in the 

 Cat, the carotid artery may pass through the foramen lacerum 

 posterius, merely grooving very slightly the petrous bone ; or 

 much more rarely, as in the Opossum, it may perforate the 

 sphenoid bone. 



In most Mammals, except the highest Apes, there is a deep 

 pit on the inner surface of the petrous bone, as in the Hare: 

 this is to receive a certain part of the brain, termed the floc- 

 cular process of the cerebellum. 



The stylo-mastoid foramen is a constant aperture, the 

 seventh nerve passing out through such an opening in the 

 petrous element wherever this is ossified in vertebrate animals. 



FIG 102 VERTICAL, LONGITUDINAL SECTION OF THE SKULL OF A PERCH. 



(After Cuvier.) 

 i frontal, ; 2, pre frontal (or lateral ethmoid) ; 3, median ethmoid ; 4, sphenitic : 



5, bisi occipital ; 6, para-sphenoid ; 7, parietal ; 8, supra-occipital ; 9, epiotic ; 



10, exoccipital ; 11, pro-otic ; 12, pterotic ; 14, ahsphenoid; 13, pre-sphenoid ; 



1 6, vomer. 



But not only the seventh nerve, but the third portion of the 

 fifth also, may perforate the same bone, as is the case in 

 Serpents, in Batrachians, and in many Fishes (e.g. the Pike) ; 

 or it may only notch it, as in Crocodiles and Birds ; or it 

 may, as in man, pass altogether in front of it. 



