OSSEOUS SYSTEM OF MAMMALIA. 



31 



of the cranium, in a strict sense, and those of the face : the former 

 encase the brain ; the latter are situated anteriorly, and more or less 

 below, forming various recesses for the lodgment of the organs of sight, 

 smell, and taste. 



As the skull encases the brain, it must be very evident that its shape 

 and dimensions will greatly depend upon those of the cerebral mass it con- 

 tains ; and, as the relative volume of this may be taken as a test of the 

 grade of intellect, the study of the skull of animals is pregnant with 



more than ordinary interest. 

 In the class to which this 

 work is restricted, the skull 

 is more or less arched, 

 or domelike, in its contour. 

 Commencing above the eyes, 

 to the chambers of which it 

 forms a projecting ledge and 

 roof above, it sweeps round 

 to its commencement, encir- 

 cling the brain, and is pierced 

 by certain apertures, or fo- 

 ramina, for the ingress of 

 arteries, and the egress of 

 veins and nerves. In Man, 

 it consists of eight bones 

 (at least in his adult condi- 

 tion), united to each other 

 by the interlocking of their 

 serrated edges, the lines of 

 junction being technically 

 termed sutures. The forehead is occupied by the frontal bone, which, in 

 the human subject, consists of a single portion, as it does also in the 

 Monkey tribes : in most Mammalia, however, it is divided by a mesial 

 suture ; such, indeed, is the case even with the human species, at an 

 early stage of existence, but it is usually (not always) closed before 

 maturity, so as to be obliterated ; whilst in these lower animals it 

 remains unconsolidated, except in certain cases, during life. 



The sides and top of the head are formed by the two parietal bones, 

 (one on each side,) joined together by the sagittal suture, and also 

 to the frontal bone by the coronal suture. The temporal bones, and the 

 wings of the sphenoid bone, also, enter into the lateral portions of the 

 skull : the back part is formed by the greatest portion of the occipital 

 bone ; the base consists of the remainder of the occipital bone (and es- 

 pecially the portion termed its basilar process, anterior to the great fora- 



Fig. 15. Lateral View of the Human Skull.-l, frontal bone; 2, 

 parietal bone ; 3, occipital bone ; 4, temporal bone ; a, mastoid process 

 of temporal bone ; 5, sphenoid bone j 6, malar bone ; 7, superior max- 

 illary bone ; 8, nasal bone ; 9, lachrymal bone, or os unguis ; 10, In- 

 ferior maxillary bone. 



