200 THE DESCENT OF MAN. 



"ures sement le lobe anterieur, une scissure psu profonde iiidique 

 "la sfiparation du lobe occipital, tres-rgduit d'ailieurs des cette 

 "Spoque. Le reste de la surface cSr^brale est encore absolument 

 "lisse." 



Tliree views of the brain are given in Plate II. figs. 1, 2, 3, of 

 the work cited, showing the upper, lateral and inferior views of 

 the hemispheres, but not the inner view. It is worthy of note 

 that the figure by no means bears out Gratiolet's description, inas- 

 much as the fissure (anterotemporal) on the posterior half of the 

 face of the hemisphere is more marked than any of those vaguely 

 Indicated in the anterior half. If the figure is correct it In no v/ay 

 justifies Gratiolet's conclusion: "II y a done entre ces cerveaux 

 '[those of a Callithrix and of a Gibbon] et celui du foetus humain 

 'une difference fondamental. Chez celui-ci, longtemps avant que 

 les plis temporaux apparaissent, les plis frontaux essayent d'ex- 

 ister." 



Since Gratiolet's time, however, the development of the gyri and 

 sulci of the brain has been made the subject of renewed investiga- 

 tion by Schmidt, Bischoff, Pansch,™ and more particularly by 

 Bcker,™ whose work is not only the latest, but by far the most 

 complete, memoir on the subject. 



The final results of their inquiries may be summed up as fol- 

 lows: — 



1. In the human foetus, the sylvian fissure is formed in the 

 course of the third month of uterogestation. In this, and in the 

 fourth mouth, the cerebral hemispheres are smooth and rounded 

 (with the exception of the sylvian depression), and they project 

 backwards far beyond the cerebellum. 



2. The sulci, properly so called, begin to appear in the interval 

 between the end of the fourth and the beginning of the sixth 

 month of festal life, but Ecker is careful to point out that, not 

 only the time, but the order, of their appearance is subject to con- 

 siderable individual variation. In no case, however, are either 

 the frontal or the temporal sulci the earliest. 



The first which appears, in fact, lies on the inner face of the 

 hemisphere (whence doubtless Gratiolet, who does not seem to 

 have examined that face in his fcetus, overlooked It) , and is either 



"plis sur le lobe frontal. II etait done bien autorlse a dire que, chez 

 "I'homme Ins circonvolutions apparai-ssent d'ct en go, tandis que cliez 

 "les singes elles se developpent d'a? en a." 



™ 'Ueber die typische Anordnung der Furchen und Wlndungen auf 

 den Grosshirn-Hemispharen des Menschen und der Affen.' 'Archiv 

 fur Anthrcpologrie,' iii., 1S68. 



™ 'Zur Entwickelungrs Geschichte der Furclien und Windungen der 

 Grosshirn-Hemispharen im Foetus des Menschen.' 'Archiv fur An- 

 thropologle,' iii.. 1868. 



