LECTURE Vr. 



141 



temporal fossse are so deep in the ape-skull that it seems as if 

 the skull had been grasped from above, behind the eyebrows, 

 and forcibly compressed : hence the zygomatic arches are more 

 distant, and the temporal ridges, to which are attached the 

 fibres of the masseter muscles, rise more towards the vertex 

 and farther behind the aperture of the ear. In some anthro- 

 poid apes, as in the gorilla and orang, there is observed, in 

 advanced age, simultaneously with the increased size of the 

 jaws, a prominent ridge, a sort of crest, on the cranium, pre- 

 senting a larger surface for the attachment of the masseter 

 muscles ; so that in these apes the whole skull is covered with 

 muscles, while in man it is in most parts only covered by the 

 scalp. 



Fiff. 44. Base of the Skull of an ancient Helvetian. 



Closely connected with the development of the jaws, is the 

 position of the zygomatic arches and of the occipital foramen ; 

 and this is at once observed in the examination of the base of 

 the skull. In human skulls the zygomatic arch always lies in 

 the anterior half of the longitudinal diameter. The external 



