74 MR. F. E. BEDDAED ON THE ['Feb. 7, 



But later Dr. Benham found this precise arrangement in the brain of 



Anihropopiihecus ccdvas and in another Chimpanzee. Whether the 

 Gorilla's brain shows the same variability or not I am unable to 

 state ; but at any rate there was no such junction in three of the 

 brains which I examined. On the other hand, in the brain of a 

 common Chimpanzee this junction was obvious on both sides. 



Calloso-marginal fissure. — This is long and deeply engraved upon 

 the brain-surface. It follows the margin of the corpus callosum 

 and bends down anteriorly with it. Posteriorly it ends with the 

 corpus callosum. So far there is no difference from the Chimpanzee. 



A number of branches arise from the upper margin of the 

 fissure and run at right angles to it towards the upper margin of 

 the brain. Two or three of these actually bend over and appear 

 right and left upon the upper surface of the hemispheres. So far 

 as concerns the parietal lobe, only one of these fissures is absolutely 

 constant ; it is to be found in all my five brains. The fissure in 

 question cuts the surface of the brain just behind the fissure of 

 Rolando. Exactly the same statement may be made with regard 

 to the Chimpanzee brain. But there is this diiference between 

 the two Anthropoid Apes, that whereas in the Gorilla the calloso- 

 marginal sulcus is continued back behind the point of origin of the 

 transverse fissure just referred to, this is at least not always the 

 case with the Chimpanzee. In two brains of the latter animal 

 which I have before me the calloso-marginal fissure ends in this 

 superficial fissure. 



Intra-p)arietal fissure. — In the Gorilla, as in the Chimpanzee, 

 this is sometimes a continuous and T-shaped fissure. The hori- 

 zontal part of the T runs roughly — in some cases, indeed, more 

 accurately — parallel to the fissure of Eolando. The stem of the T 

 joins the Simian fissure behind. 



Dr. Cunningham divides this complex fissure in the human 

 brain into four separate ones, since in the foetal brain they are not 

 confluent. In the Gorilla that portion of the system which 

 Cunningham terms " sulcus postcentralis superior," and which lies 

 most mesially of the various component parts, is sometimes 

 separate from the rest. This was the case with the right half of 

 the brain belonging to the College of Surgeons (fig. 1), in which, 

 moreover, the furrow in question was prolonged anteriorly to reach 

 the fissure of Rolando. The same arrangement was observed in 

 the same hemisphere of a second brain (fig. 5) and in the left 

 hemisphere of a third (fig. 7), save that in neither of these was 

 there a junction with the fissure of Rolando. In two other brains 

 these various sections were confluent. 



There is thus in the Gorilla precisely the same variability in 

 respect of these fissures that occurs in the Chimpanzee. It is no 

 more the " usual condition " in the Gorilla than it is in the 

 Chimpanzee for the sulcus postcentralis superior to be confluent 

 with the rest of this system of fissures. 



Sulci of tlie frontal lobe. — It may be convenient to describe these 

 furrows in some elaboration in a given brain and then to describe 



