1 68 CHORDATE ANATOMY 



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. See Fig. 158. 



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 

 lie 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. 



The Human Skull. The human skull consists of twenty bones of which 

 eight form the cranium or brain-case and the remaining twelve make the 

 facial skeleton. The eight bones of the cranium are the frontal, occipital, 

 ethmoid, sphenoid and the paired parietals and temporals. The facial 

 skeleton includes the mandible and vomer, and the paired maxillaries, 

 zygomatics (malars), nasals, lacrimals, and palatines. Since the turbinal 

 bones of the nose are extensions of the ethmoid they are not counted as 

 separate bones. A comparison of the mammal skull with that of man 

 reveals that the bones are homologous. 



Development of the Cranium. The history of the vertebrate skull 

 revealed by the study of its comparative anatomy is amply supported 

 by its embryology. Both prove it to be a complex formed by the union 

 of diverse elements, capsules that contain the sense organs, supports for 

 the gills, and underpinning and protective covering for the brain, while 

 in the occipital region vertebrae appear to have fused with the brain 

 case. The primordial cartilaginous cranium of the human embryo arises 

 as a pair of parachordal cartilages and a pair of prechordal cartilages or 

 trabeculae. These fuse together; later they combine with two pairs of 

 sensory capsules, the olfactory and the auditory. This formation of the 

 cartilaginous basis of the cranium, the chondrocranium, takes place 

 during the second month of intra-uterine Ufe. Ossification from separate 

 centers begins with the third. See Fig. 149. 



Evidence from comparative anatomy proves that the bones of the 

 human skull correspond to a much larger number of separate bones which 

 appear in the fishes and have been progressively reduced by fusion with 



