490 



COMPARATIVE PHYSIOLOGY. 



even distinction in the intellectual world; and though idiots 

 have been known to possess brains abnormally heavy, it is 



Fig. 350. 



Fig. 349.— Outer surface of brain of horse (after Solly and Leuret). e, olfactory lobe; 



h, Mppocampal lobe (processus pyriformis); 1, 2, 3, lobes of cerebellum; o, optic 



nerve; m, motor oculi; p, fourth nerve; t, fifth nerve; «, sixth nerve; /, facial; 



I, auditory; g, glosso-pharyngeal; v, vagus; *, s'pinal accessory; re, hypoglossal; 



X, pons Varolii. 

 Fig. 350. — Longitudinal section through center of brain of horse, presenting view of 



internal surface (after Solly and Leuret). c.c, corpus callosum; p, thalamus; CO, 



middle commissure; t. q, corpora quadrigemina, in front of which is the pineal 



body. The cerebellum has been cut through. 



nevertheless true that brain-weight and the higher powers of 

 man bear a close though not invariable relationship. The 

 apparent discrepancies are susceptible of explanation. 



Besides the gray matter, with its cells of highest functional 

 value from the standpoint now taken, the brain consists, and 

 in large part, of neuroglia and nerve-fibers, with probably 

 ohieflyj and in the case of the fibers solely, a conducting func- 

 tion. 



