Editorial. ix 



index is 29.6. In the lower apes the central index is higher than in 

 the anthropoids. 



19. In man the field of the insula shows marked changes with 

 reference to the cranial wall during intra-uterine life. More and 

 more of its area comes to lie under cover of the parietal bone, and 

 relatively less under cover of the frontal bone, as development pro- 

 ceeds. In the adult the coronal line cuts the insula in such a manner 

 that 13 per cent, of its length lies in front of it, and 87 per cent, be- 

 hind it 



20. In the chimpanzee and the low apes no part of the insula 

 lies in front of the coronal line ; m the orang the upper and anterior 

 corner of the insula projects slightly in front of this line. 



21. In the human infant and young child, as well as in the ape, 

 the point at which the stem of the Sylvian fissure reaches the outer 

 surface of the hemisphere is situated relatively further back than in 

 the human adult. 



22. The Sylvian fissure is relatively longer in the left hemisphere 

 than in the right, and in the ape than in man." * * * 



" 28. In the cebus the Sylvian fissure lies above the level of the 

 squamous suture ; in the macaque, homadryas and orang, it lies im- 

 mediately subjacent to the fore-part of the suture; in Cynocephalus 

 anubis and the chimpanzee the fissure is situated in its fore part be- 

 low the level of the front part of the suture. 



29. The relative depth of the parietal and temporal lobes in the 

 lower apes resembles that in the human child ; in the anthropoid ape 

 the relative parietal depth of the hemisphere exceeds that in the hu- 

 man adult." 



The Fissure of Rolando. 



Cunningham found that in 60 per cent, of the brains examined 

 the upper end of the fissure of Rolando turned over the mesal border 

 of the hemisphere ; in 19 per cent, its ventral end was connected by 

 a shallow transverse sulcus with the Sylvian fissure. The fissure of 

 Rolando appears in two parts, the lower two thirds appears before 

 and independent of the upper third. The relative position of the 

 fissure of Rolando is remarkably constant. The upper fronto-Ro- 

 landic index is 53.3, the lower 43.3. In anthropoid the upper end of 

 the fissure of Rolando is placed relatively farther back than in man. 

 The average Rolandic angle in the human brain is 71.7. The average 

 relative length of the fissure of Rolando is 39.3. 



