THE SKELETAL SYSTEM 225 



cranium. Among other changes is an increase in the facial angle from 

 an acute to a right angle. The facial angle is the angle between a line 

 from the frontal bone to the maxilla and one from the basioccipital to the 

 base of the nasal septum. Apes and fossil species of men, however, help 

 to bridge this contrast. See Fig. 184. 



The heavy superciliary crests characteristic of the chimpanzee and 

 gorilla, but lacking in modern species of men, are present in fossil Neander- 

 thal and Rhodesian man. Furthermore, the usual contrast between apes 

 and man disappears in the orang-utan which, like modern man, has rudi- 

 mentary superciliary ridges. Furthermore, the contrast between the 

 skulls of apes and man holds for the adult only, not for the young, the 

 differences increasing with age. 



Against the evolution theory as applied to the human species it used 

 to be urged that there are no connecting links between man and apes, 

 contrary to expectation if man and apes have evolved from a common 

 ancestry. The contrast in brain size between man and apes is especially 

 striking. The brain of the gorilla is never larger than 600 cc, while the 

 smallest human brain is not less than 1000 cc. and the normal male brain is 

 1400. The discovery of the cranium of the Java man with a brain 

 capacity of between 800 and 900 cc. helps to reduce this contrast. The 

 striking fact revealed by fossil human skulls is that the characteristics 

 which distinguish them from the skulls of modern man tend to bridge 

 over the gap between man and apes. In other words, all fossil skulls, 

 except that of the Cro-Magnons which is like that of modern man, are 

 more ape-like than those of modern races. The dental arch of Negroid 

 races is intermediate between that of apes and Europeans. The chin 

 which is such a striking feature of the modern human jaw is lacking in 

 some fossil men as in the great apes. 



Another contrast between the skull of man and apes is in the relation 

 of the skull to the backbone. The skull of modern man is poised on the 

 occipital condyles at about its center of gravity, but the condyles of apes 

 lies far behind the center of gravity of the head. Therefore are the neck 

 muscles of modern man relatively weak, those of the ape massive. It is 

 an interesting fact from the evolutionary point of view that the skull of 

 Neanderthal man shows an intermediate condition. 



Bones of the Cranium. Eight bones in man enclose the brain, frontal, 

 occipital, ethmoid, and sphenoid and the paired parietals and temporals. 

 The facial skeleton includes twelve bones, the lower jaw or mandible, 

 the vomer, and the paired maxillaries, zygomatics, nasals, lacrimals, and 

 palatines. Since the turbinal bones of the nose are extensions of the 

 ethmoid they are not counted as separate bones. 



The frontal bone forms the front of the cranium. Ridges of this bone 

 above the orbits of the eyes are the superciliary crests. Within the 



