308 ORIGINAL ARTICLES. 



usually be recognized iu the human brain, by tracing outwards from 

 the longitudinal fissure, the internal vertical fissure, which is always 

 present, though thrust backwards at its upper end by the enlarge- 

 ment of the parietal lobe, so as to be somewhat oblique instead of 

 vertical. On the internal surface of the hemispheres of the Chim- 

 panzee, thefronto-parietal and. quadrate lobes are seen to occupy the 

 space in front of this fissure, a small internal occipital lobule lies behind 

 it, and the temporo-occipital lobe is at once distinguishable, below the 

 anterior portion of the fissure of the hippocampus. As thus defined, 

 it is impossible to escape from the conviction that all the above- 

 named parts exist in the Chimpanzee, as well as in man ; and that, 

 amongst others, the little occipital lobules at the posterior extremity 

 of each hemisphere, in the former, are the homologues of those in the 

 latter. "We shall see that this conclusion is fully supported by the 

 closest scrutiny of the convolutions, and of the internal structure of 

 the cerebrum. 



As to the convolutions in the Chimpanzee's brain, one can hardly 

 pay a better tribute to M. Gratiolet's general accuracy, than to 

 adopt his description of them, whilst referring to our own specimen. 

 After pointing out the general characters of the frontal, parietal and 

 occipital lobes, a remarkable notch which interrupts the border of 

 the orbital surface, (seen in our fig. 4), the large size of the occipital 

 or posterior lobe, and the even or perfect edge of its operculum, 

 figs. 4, 5, in front of 10,10', he proceeds thus, p. 50 : — 



" The convolutions of the frontal lobe are very large, even larger and wider 

 than those of the Orang. The superior frontal convolution* (figs. 3, 3', 4 and 5,) is 

 subdivided into two parts, of which the highest is marked by secondary sulci. 



" The middle frontal convolution, 2, is well marked. The inferior frontal or 

 supraciliary convolution, 1,1, is very large, and broadly designed, so that the frontal 

 lobe is well developed in all its parts. 



" '\"he first ascending convolution, 4,4, is slender, flexuous, and only slightly in- 

 clined backwards : it presents no marginal notches, and its surface is absolutely 

 smooth. 



" The second ascending convolution, 5,5, is equally simple and smooth; it passes 

 up by the side of the preceding one, forming parallel flexuosities with it; but having 

 reached above the bent convolution, 6, (pli courbe), it forms an elbow, and spreads out 

 into a large lobule, 5'5", which is prolonged back to the external perpendicular 

 fissure. This lobule, [named by M. Gratiolet the lobule of tlie second ascending 

 convolution^ is very elegantly subdivided by a rather complicated sulcus, which serves 

 to separate two distinct convolutions, one external, 5 ', the other internal, 5". The 

 external convolution pursues a very simple course; but the internal one is folded 

 several times upon itself, an arrangement which is tolerably constant. _ 



" The commencement of the lent convolution (pli courbe), 6,6', is remarkable. 

 In the Orang and in the Gibbon, it begins at the top of the Sylvian fissure. In the 

 Chimpanzee, it arises in front of the summit of that fissure by a large extremity, fig. 

 4, and describes a very extensive curve around it. 



" As to the descending part, 6', of the bent convolution, it is very slender, 

 scarcely flexuous, and rather long, * * * * 



" The convolutions of the temporal lobe, are very simple, * * * * . [They are 



* We substitute here the references to our figures, for those given by M. Grati- 

 olet to his. The italics are in the original. My own additions are between brackets []. 



