220 STUDY OF BRAINS OF SIX EMINENT SCIENTISTS AND SCHOLARS. 



likeness to our species. Their use of the hands and arms and their facial expressions 

 are quite human. In their intellectual recognition of things they are far superior to 

 the lower animals and as they most closely approach man in their mental character- 

 istics we are naturally interested in the architecture of their brain and the mechanism 

 of their mind. 



Whatever series of organs is studied and compared, complete justification is found 

 for the claim that the Primates — the highest order of mammals so named by 

 Linnaeus 170 years ago — form a natural monophyletic group. I will not attempt 

 here to discuss the inter-relations of the subgroups or recite the prevailing inferences 

 as to the genealogical tree of man. Suffice it to say that these inferences are yearly 

 amplified and strengthened by new finds in morphological and paleontological lines 

 of research. At all events the tailless apes show in their development the immediate 

 transition to the human form. One species may be nearest to man in the number of 

 ribs as the orang, or in the character of the cranium, dentition and proportional size 

 of the arms, as the chimpanzee. The gorilla is nearest to man in the proportions of 

 the leg to the body and of the foot to the hand, in the curvature of the spine, form of 

 the pelvis and absolute cranial capacity. The gibbon of all the Anthropomorpha is 

 most remote from man, but its erect attitude, its femur and other skeletal parts are 

 more human than in any other genera. Then there are several fossil forms apparently 

 belonging to this group, from DryopUhecus (Middle Miocene) to the Pithecanthrojms in 

 which human characters preponderate. But while fossil specimens of bones and teeth 

 are rare enough, the perishability of the brain renders its natural preservation prac- 

 tically impossible and we are compelled to draw our own inferences concerning the 

 morphology of this organ from a comparison of the brains of modern living forms, 

 assisted by studies of the cranial configuration of extinct types. 



Embryological studies are of the greatest aid in elucidating many otherwise 

 obscure stages in development. Thus it is seen that the human and anthropoid cranial 

 form is the universal embryonic norm from which the skulls of all mammals develop. 

 Every skull at or near the time of birth is orthognathic, that is, the facial angle 

 approximates a right angle, and each has a tendency to become more and more prog- 

 nathic, a type of skull in which the jaws are larger and more prominent. In the 

 gorilla and orang, less so in the chimpanzee, it becomes very prognathic, but in man 

 it is checked by anatomical correlations. The development of the jaw is more or less 

 closely associated with the size of the teeth and consequently with the nature of the 

 diet ; the bulk of the masticatory muscles and the temporal area is greater in the 

 more prognathic, heavy-jawed skulls, for the temporal muscle must be larger to over- 

 come the mechanical disadvantages of the longer lever. This muscular influence 



