68 THE ANATOMY OF VERTEBEATED ANIMALS. 



tlie' only sulcus presented by the Rabbit's brain is that 

 deep and broad depression (H), which runs parallel ■\^'ith the 

 posterior pillar of the fornix, and gives rise, in the interior 

 of the descending cornu of the lateral ventricle, to the 

 projection which is termed the liippocampus major. In 

 the Pig, this Mppoccmvpal sulcus {H) is much narrower and 

 less conspicuous ; and a marginal {M) and a callosal (C) 

 gyrus are separated by a well-marked calloso - marginal 

 sulcus. As in the Rabbit, the uncinate gyi'us forms the in- 

 ferior boundary of the hemisphere. In the Chimpanzee, the 

 marginal and callosal gyi'i are still better marked. There 

 is a deep internal perpendiciilar, or occipito-imrietal, sulcus 

 {Lp). The calcarine sulcus {Ca) causes a projection into 

 the floor of the posterior comu, which is the hippocampus 

 viinor ; while the collateral sulcus (Coll) gives rise to the emi- 

 nence of that name in both the posterior and descending 

 cornua. The hippocampal sulcus (H) is relatively insigni- 

 ficant, and the lower edge of the temporal lobe is formed by 

 the posterior temporal gyrus. 



In the Rabbit, the corpus callosum is relatively small, 

 much inclined upwards and backwards ; and its anterior 

 extremity is but slightly bent downwards, so that the so- 

 called genu and rostrum are inconspicuous. The Pig's 

 corpus callosum is larger, more horizontal, and possesses 

 more of a rostrum : in the Chimpanzee, it is still larger, 

 somewhat defiexed, and very thick posteriorly ; and has a 

 large rostrum. In proportion to the hemispheres, the 

 anterior commissure is largest in the Rabbit and smallest 

 in the Chimpanzee. The Rabbit and the Pig have a single 

 corpus mamtnillare, the Chimpanzee has two. The cere- 

 bellum of the Rabbit is very large in proportion to the 

 hemispheres, and is left completely uncovered by them in 

 the dorsal view. Its median division, or vermis, is straight, 

 symmetrical, and large in proportion to the lateral lobes. 

 The flocculi, or accessory lobules developed from the latter, 

 ai'e large, and project far beyond the margins of the lateral 

 lobes. The ventral face of the metencej)halon presents 

 on each side, behind the posterior margin of the pons 



