THE NERVOUS SYSTEM 131 



brain weight at 425,25 grs., the relative weight of the latter 

 would be 1 : 220 (Moller). 



A comparison of the cerebral surface shows that Man 

 differs from the Anthropoids in the preponderance of the 

 frontal lobe (/>., Figs. 78-82) and, to a lesser degree, of the 

 occipital lobe (pc.\ and in a corresponding backward extension of 

 the temporal lobe (tp.}. The parietal lobe (pa.') is about equally 

 developed in the brains of Man and of Anthropoids (Moller). 



Since this subject has so far been, comparatively speaking, 

 little investigated, and since our knowledge of the functional 



*/. c.h. e P-f; b c - p '"f *' cf. A.6. 



. cr - ch- 



op. \ 



id. 

 FIG. 83. HYPOTHETICAL MEDIAN-LONGITUDINAL SECTION THROUGH THE SKULL 



AND BRAIN OF A VERTEBRATE EMBRYO. (Partly after Huxley.) 



cr'., basis cranii ; ch., chorda dorsalis ; cr"., roof of the skull ; na., nasal cavity ; c.h., 

 cerebral hemisphere, with the corpus striatum (c.s.) lying basally, and the olfactory 

 lobe (ol.) anteriorly ; f.b., thalamencephalon (fore-brain), which has been produced 

 dorsally into the pineal gland (ep.\ and basally into the infundibulum (if.), lip., the 

 hypophysis. Anteriorly, the base of the optic nerve (op. ) is seen, and in the lateral 

 wall the position of the optic thalamus is indicated (th. ) ; c.p., posterior commissure ; 

 m.b., mid-brain ; h.b. , hind-brain ; c.c., canalis centralis. 



significance of the different regions of the brain is still far from 

 complete, no general conclusions as to the possible correlation 

 of these differences with mental peculiarities can be drawn. 



The slight projection of the cerebellum from below the 

 edges of the occipital lobes in Anthropoids, is due less to the 

 narrowness of the latter than to the striking breadth of the 

 cerebellum itself (Moller). Even in man the occipital lobes do 

 not always completely cover the cerebellum, but in this matter 

 considerable variation occurs. 1 



Special interest attaches to the pineal gland (epiphysis cerebri) 

 (ep., Figs. 84 and 86) which arises in the region of the roof of 

 the fore-brain. 



In the lower Vertebrates this organ either lies free or is 

 embedded in a depression or foramen (parietal foramen) of the 

 1 It must be left to future investigators to prove whether the topography of the 

 course of the fibres in the optic chiasma given by Joh. Moller for Anthropoids, i.e. 

 the constant occurrence at the surface of certain groups of fibres, has a parallel in 

 Man (perhaps in embryos or the lower races). 



