1865.] 



Notes and Correspondence. 



563 



a very regular, rather broad, oval ; 

 when viewed thus in the skull after 

 the removal of the calvarium, no 

 ■portion of the cerebellum is visible, 

 the cerebrum completely covers it and 

 overlaps it to an easily appreciable 



extent. The convolutions of the 

 upper face are drawn in Fig. 1. It 

 will be observed that the two he- 

 mispheres are nearly symmetrical 

 with regard to the disposition of the 

 sulci, though not completely so. I 

 found, however, that in my speci- 

 men the differences between the two 

 hemispheres were identical with 

 those given by Gratiolet in his 

 figure. The parts lettered a, b, c, 

 are the three portions of the frontal 

 region, respectively inferior, middle, 

 and superior. The large develop- 

 ment of the superior frontal region 

 is a sign of elevation in monkeys — 

 as the greater comparative size of 

 this part of the brain in man is one 

 of the chief points of difference be- 

 tween him and the higher apes. The 

 Orangs, Gibbons, and Semnopi- 

 theci, have this portion of the brain 

 developed to a greater extent than 



the series formed by the Chimpan- 

 zee, Macaci, &c, and hence, perhaps, 

 the Orang should be placed nearer 

 to man than the Chimpanzee, while 

 the Semnopithecus would hold a 

 higher place than the correspond- 

 ing forms in the other series. The 

 parts marked d, e, e', /, form the 

 parietal region of the brain, d being 

 " the first ascending convolution," 

 e " the second," e' " the lobe of the 

 second ascendiug convolution," and 

 / " the curved convolution." The 

 fissure separating the curved convo- 

 lution from the lobe of the second as- 

 cending convolution is well marked 

 in the Entellus, and is immediately 

 connected with the deep incision 

 which separates the parietal from 

 the occipital region i, j. In the 

 sketch, only the superior and middle 

 portions of the occipital region are 

 visible ; its inferior portion is si- 

 tuated below, and is partially seen 

 in the lateral view of the internal 

 face (Fig. 2). 



Above the letter g in Fig. 1, 

 which marks the inferior marginal 

 convolution, is the fissure of Syl- 

 vius, separating the tempero-sphe- 

 noidal region of the brain from the 

 parietal. In the Semnopitheci the 

 fissure of Sylvius is free and open 

 throughout ; in the allied Cercopi- 

 theci its summit is hidden under 

 the folded convolution f. The mid- 

 dle temporal convolution h, and the 

 inferior marginal g are all that are 

 visible of the tempero-sphenoidal 

 lobe on the superior surface. 



The principal fact which is obser- 

 vable on comparing the brain of 

 this monkey with the drawings 

 and descriptions of the brains of 

 Gibbons and Cercopitheci, is that in 

 the Semnopithecus there is a deve- 

 lopment of the frontal region inter- 

 mediate between what is observable 

 in these two : as Gratiolet says 

 " the frontal lobe is advanced to- 

 wards the posterior parts of the 

 brain ; the anterior region is de- 

 veloped at the expense of the 

 posterior;" thus indicating an ad- 

 vance on the brain of the Cercopi- 



2 Q2 



