Ill] Points nil tin Aiiilfnii/i/ of flic /'Yx.s-mv of h'nfniK/n '2:', 



Next, concerning tlic representation of this anneciant in the ape, liv 1'rolessor Sherrington's 

 kindiK'ss, I have been permitted to examine all tlic anthropoid brains in his possession, which 

 include specimens taken from the gorilla, orang and chimpanzee. Qnfortunately several of 

 these had been hardened for cither |iur|iiises. and it was therefore impossible to <ijicn up the 

 Uolandic fissure without injuring the specimen: still, in every instance in which a view of 

 the Hssural wall could be obtained, an elevation was invariably identified on the frontal side 

 homologous with that in the human being; the buttress, however, was relatively slender, and 

 the degree of shallowing which it gave rise to comparatively slight, and in no case was there 

 anything further than a very slight attempt at an interruption of the fissure; I further satisfied 

 myself that it had a constant relation to the upper genii, and that it was mainly responsible 

 for the production of this bend: I also noticed that its position was rather variable, and 

 especially that it had a tendency to slide down the lateral face of the hemisphere somewhat 

 further than it does in the human brain, so that it would be more exact to say that on the 

 average it lay slightly below rather than at the junction of the upper and middle thirds 

 of the fissure. 



Cunningham also has observed this buttress in the brains of the chimpanzee and orang, 

 but states that it is not very distinct in the latter. 



Not having examined a sufficiency of specimens, I do not feel entitled to give a description 

 of variations in the buttress formation which probably exist in the different members of the 

 anthropoid family: for the present, let the statement suffice that such a structure does exist, 

 and later on, when we consider the histology and function of the part, I may be able to show 

 that the anatomical parallelism is produced by the operation of similar factors in both man 

 and ape. Without further comparative investigation I also withhold an opinion as to whether 

 the interrupted fissure of Rolando is a phylogenetic relic, as well as an expression of imperfect 

 development. 



Concerning other annectant gyri or buttresses in the fissure of Rolando, I need oiilv mention. 

 that such do exist towards the lower end of the fissure, but they do not require special description; 

 they are not anything like so prominent as the upper buttress, they do not rise to the surface, 

 and they are very inconsistent in both number and position, all apparently due to the fact 

 that they are infoldings of the fissural wall, dependent on the presence of surrounding sulci. 

 Just as these buttresses vary, so also the inferior genii, compared with the superior, is a very 

 unstable element. 



It would lie interesting to know whether any structure can be defined in animals lower 

 in the mammalian series, which might be considered the homologue of the large upper Rolandic 

 annectant. Physiology has of course suggested that the unions cruciatus of the dog is the 

 equivalent of the Kolandic fissure, but Elliot Smith has come to the conclusion that the crucial 

 sulcus (not only of the dog but other animals) is the homologue of the upper or dorsal part 

 of the central sulcus, and that the lower or ventral part of the latter is formed either from, 

 or at the expense of, the caudal extremity of the coronal sulcus, in which case the large field 

 between the cruciate and coronal sulci (in the dog) would have to be regarded as the equivalent 

 of the annectant 1 . 



1 Since this was written, I have made a complete examination of the brains of Cains and Felis, and, as a 

 rissuret on the hinder limb of the sigmoid gyms, known as thr compensatory ansate fissure, forms a dividing line 

 lu-tween Betz cells and what I take to be post-central or sensory cortex, I now regard this element, and not the 

 sulcus cruciatus, as the equivalent of the upper segment of Rolando. (Vide addendum.) 



