MORPHOLOGY OF THE CEREBRAL CONVOLUTIONS. 265 



to the division given by Gratiolet, except that he includes the four external plis de 

 passage, which Gratiolet placed in the occipital lobe. The boundaries of the occipital 

 lobe are, according to Bisehoff, very indistinctly marked. He regards it as filling 

 up that part of the occipital bone above the tentorium and inferiorly extending to 

 the upper angle of the pyramid of the petrosal bone. The separation on the mesial 

 surface from the parietal, is as is generally recognized, by means of the fissura per- 

 pendicularis interna or parieto-occipital. Inferiorly, he considers that the occipital 

 lobe passes farther forward than it does at its upper border. This inferior anterior 

 border is a shallow depression, recognized only in the entirely fresh and not yet 

 softened brain, produced by the upper edge of the petrosal ridge. It corresponds to 

 the anterior edge of the hemisphere of the cerebellum. He remarks, however, 

 that this lower boundary is not distinctly given because the convolutions of the 

 occipital lobe fuse with those of the temporal lobe. He believes, nevertheless, that 

 this, boundary is marked by distinct furrows, and is also indicated by the course of 

 the arteries. He does not recognize the separation on the lateral surface from the 

 parietal lobe, by means of the fissura perpendicularis externa, for he believes that 

 in the adult human brain this fissure is wanting. The boundaiy is, according to 

 him, only indicated by an ideal line descending from the upper extremity of the 

 fissura perpendicularis interna, obliquely forward to the lower edge of the hemis- 

 phere and by a frequently noticeable nick, the convolutions of the parietal and 

 occipital lobes fusing with one another. With regard to the boundaries of the tem- 

 poral and Stammlappen (island of Reil) he does not differ from previous writers, 

 except as to the posterior boundaries of the temporal lobe. 



Ecker, in his division of the cerebral hemispheres into lobes, does not differ 

 from those who have preceded him. He recognizes the usual five lobes, frontal, 

 parietal, occipital, temporal and central. These he considers as more or less 

 separated from one another by three fissures, the fissura Sylvii, fissura centralis 

 and fissura parieto-occipitalis. 



The English anatomists, Turner, Huxley, Marshall, Flower, Rolleston, etc., 

 in their descriptions of the brain have followed the divisions of Gratiolet and Ecker. 



Before proceeding to the new views which the author proposes to apply in 

 studying the morphology of the primate brain, it will be necessary to outline as 

 briefly as possible the topography and nomenclature of the cerebral surface as it is 

 accepted at the present time. This is absolutely essential, since without it, it 

 would be impossible to comprehend the extensive changes as regards the general 

 arrangement and relations of the cerebral fissures and convolutions which the 

 author has to offer. In preparing this general account the author is much indebted 

 to Ecker's work on the convolutions of the human brain, 1 and to Clevenger's Cere- 

 bral Topography, 2 which works have been closely followed. 



1 Die Hirnwinduugeu des Menschen, etc., 2d ed., Braunschweig, 1888. 



2 Journal of Nervous and Mental Disease, October, 1879. 



