NERVOUS SYSTEM. 241 



are greater in size, more cineritious externally, and contain 

 wider prolongations of the lateral ventricles in herbivorous 

 than in carnivorous quadrupeds. The lateral ventricles 

 always present the anterior and inferior cornua, the choroid 

 plexus, and the to3nia semicircularis between the thalami and 

 the corpora striata. The great transverse commissure of the 

 cerebral hemispheres, the corpus callosum, is here at its max- 

 imum of development, as are also the anterior and posterior 

 commissurse cerebri and the fornix, and we can always per- 

 ceive the hippocampus major, the septum lucidum between 

 the lateral ventricles, and the pineal gland with its two pe- 

 duncles. The cineritious matter is now less abundant on 

 the surface of the brain proportionally to the white fibrous 

 part within, and the external convolutions, which are still 

 wanting on the smooth bird-like brains of the montrema and 

 the rodentia, are very superficial in the cetacea, edentata, 

 ruminantia, and pachyderma. The convolutions penetrate 

 deeper in the large expanded hemispheres of carnivora, qua- 

 <lrumana and man, where we observe also the cerebrum to 

 pass more and more backwards over the cerebellum. The 

 symmetry of the convolutions on the two cerebral hemi- 

 spheres is most distinct where they are few and deep, as in 

 carnivora and quadrumana, and the laminae of the cerebellic 

 hemispheres encrease in number and depth as we ascend to 

 man. The brain of herbivorous quadrupeds is thus distin- 

 guished by several indications of inferior development from 

 that of carnivorous species, as seen in comparing the brain 

 of the pecari, Dicotyles torquatus, (Fig. 99. A,) with that of 

 the lion, Felis leo, (Fig. 99. B.) In the herbivora the spinal 

 chord and medulla oblongata (99. A. #, b,) are larger and 

 broader, compared with the cerebral parts which lie before 

 them, than in the carnivora (99. B. a, b,) and in the carnivora 

 the corpora pyramidalia (99. B. b } ) the crura cerebri (99, B. d,) 

 the cerebral hemispheres (B. #, h,) the corpus callosum, the 

 cerebellic hemispheres (B./,/,) and the tuber annulare (B.c,) 

 are proportionally larger than the corresponding parts in the 

 vegetable-eating quadrupeds (99. A.) The convolutions are 

 more superficial on the narrow and short cerebral hemi- 

 spheres of the pecari, (99. A. g, h,) the hollow olfactory tu- 

 bercles or processus mammillares (99. A. 7c,) communicating 

 by wide canals with the lateral ventricles, are larger ; the in- 



PART III. R 



