THE BRAIN. 



487 



in the largest specimens, the brain of man is even absolutely 

 heavier than that of any other animal, which is in great part 

 due to the preponderating development of the cerebrum. 



WhUe the cerebral surface is smooth in all the lower verte- 

 brates, and but little convoluted until the higher mammals are 

 reached, the brain of the primates, and especially of man, has 

 its surface enormously increased, owing to its numerous fis- 

 sures and . convolutions, which, in fact, arise from the growth 



- Flo. 341. — Brain and spinal cord of frog (Bastian). A, olfactory lobes; B, cerebral 

 lobes; B, pineal body; C*. i?, optic lobes; E, cerebellum; H, spinal cord. The 

 cerebellum is notably small. 



of the organ being out of proportion to that of the bony case 

 in which it is contained ; and since those ceUs which go to 

 make up the gray matter and are devoted to the highest func- 

 tions, are disposed over the surface, the importance of the fact 

 in accounting for the superior intelligence of the primates, 



Fig. 348. 



Fig. 343. 



Fig. 342.— Brain of the pike, viewed from above (Huxley). A^ the olfactory nerves or 

 lobes, and beneath them the optic nerves; B, the cerebral hemispheres; C, the 

 optic lobes; I), the cerebellum. 



Fig. 343.— The brain of edible frog {Bana esculenta"). 1x4. (After Huxley.) L. ol, 

 the rhinencephalon, or olfactory lobes, with /, the olfactory nerves; Sc, the cere- 

 bral hemispheres; j'A. o, the thalamencephalon with the pineal gland, i^; L.op^ 

 optic lobes; C, cerebellum'; S. rh^ the fourth ventricle; Mo^ medulla oblongata. 



