MARSHALL OX TIIE BLAIN OF A YOUXO CHIMPANZEE. 303 



Schroeder van der Kolk's and Yrolik's corresponding view, in both 

 of which the characters of the lateral aspect of the Chimpanzee's 

 brain are entirely lost ; the cerebellum and medulla are pressed hori- 

 zontally backwards, so that the former is tilted up and projects too 

 far behind, and converts the natural!}- concave lower border of the 

 cerebrum, from the middle lobe backwards, into an even oblique line. 

 The same criticism must apply, we think, to the lateral view of the 

 Orang's brain, given by Dr. Rolleston, the obliquity which he notices 

 in his paper (p. 20G) being evidently the result of displacement 

 from pressure. 



The comparison of the Chimpanzee's brain, as seen in. front and 

 behind, with the human brain, does little more than confirm the ob- 

 servations already made. Anteriorly, in the ape, the want of depth 

 and width of the frontal region, and the hollowing of the orbital sur- 

 faces ; and, posteriorly, the want of height in proportion to the 

 width, and the smoothing down of the parietal regions, as contrasted 

 with the towering height and width of those parts in man, are chiefly 

 noticeable ; so that the Chimpanzee's brain has a more compact, 

 rounded, form. We do not observe, in this animal, the wall-sided 

 shape of the lateral regions, mentioned by Dr. Eolleston as cha- 

 racteristic of the Orang, the sides of the cerebrum being very evenly 

 convex. In the posterior view, the cerebellum of the Chimpanzee 

 appears very wide in proportion to the cerebrum ; but it is shallow and 

 less full and rounded, than in man ; it is distinctly overlapped by the 

 cerebral hemispheres, on each side, but rather less so, than in the 

 human brain. 



On the base of the Chimpanzee's brain, (see figs. 1 and 2,) the de- 

 ficient length and width, and the pointed character of the frontal re- 

 gion, anteriorly, as compared with man's, are very evident : the orbital 

 surfaces are extremely concave, and the median ridge,- on each side of 

 the longitudinal fissure, disproportionately prominent. The under 

 surfaces of the cerebral hemispheres, from the point of the middle lobes 

 to the hinder extremities of the cerebrum, are relatively shorter, and 

 appear more incurved, or kidney-shaped, than in the human brain. 

 The line of greatest width of the base of the brain, in the Chim- 

 panzee, is half an inch nearer to the posterior, than to the anterior 

 end of the hemispheres, lies just in front of the widest part of the 

 cerebellum, and passes across just behind the pons Varolii ; whereas 

 in man, it is placed proportionately further back, namely, 1\ inch 

 nearer to the occipital, than to the frontal, extremity, lies considerably 

 in front of the widest part of the cerebellum, and passes across a 

 little behind the pons. The cerebellum itself appears flatter, and is 

 much wider, in proportion to its length, from before backwards, and 

 also, in proportion to the extreme width of the cerebrum, in the 

 Chimpanzee, than in man, in whom it is more protuberant, and 

 though absolutely wider, less so in proportion to its other dimensions, 

 or to the width of the cerebrum. The greater relative size of the 

 cerebellum in this ape, depends therefore, mainly, on its greater rela- 



vol. i. — x. h. k. 2s 



