50 THOMAS DWKllIT OX 



and then, rising sharply, is continued as the second temporal convolution. Tliis a]iplies 

 to both sides. 



The temporal lobe, so far as seen on the outside, requires little description. The 

 parallel fissure below the first temporal convolution is, as seems always to be the case in 

 the chimpanzee and in all the higher primates, remarkably clear and simple. It ends 

 above with a bifurcation, around the lower branch of which the angular gyrus has to 

 turn to reach the second temporal convolution as just described. The first temporal 

 convolution is .self evident. The second and third seem to be somewhat fused on both 

 sides. Those on the nnder surface of the lobe will be -con.sidered later. 



The occipital lobe, as seen externally, is marked by the large size and extreme 

 simplicity of its convolutions. It looks like an undifferentiated mass on which a capital 

 tH has been imprinted, lying on its side with the stem forward. Tins is the s. occipitalis 

 obliquus. 



The gyrus occipitalis secundus (the operculum) lies behind the Atfenspalte and joins 

 the angular gyrus; before doing so, however, it is itself joined by the thii-d occipital 

 which lies under the ^ . Beneath this runs the sulcus occijntalis inferior just above 

 the lower edge of the hemisphere. This fissure is well marked on both sides, giving off 

 a vertical ascending branch, round which the second temporal convolution turns. On the 

 right the middle part of this fissure is not visible from the side. 



The median surface of the brain and the inferior aspect of the occipital and temporal 

 lobes remain to be described. The Jissura cnlloso-marginalis is very simple and so like 

 that of the human Ijrain that detailed description is needless. It begins on the right 

 hemisphere far l)iick on the mesial surface of the frontal lobe, and is uninterrupted. On 

 the left the plan is much like that figured by Kiikenthal and Ziehen. There is below 

 a sulcus rostralis with which the calloso-marginalis is joined by a little fissure so minute 

 and shallow that the junction is more apparent than real. Behind its termination is 

 the lohulus quadratus which is connected with the arcus parieto-occijntalis above and 

 with the gyrus fornicatus below. Tlie last named convolution and its continuation, the 

 gyrus hypocampi, are uninterrupted on the right. On the loft it is divided by the 

 Jissura ccdcarina. The uncus is well marked. 



The internal parieto-occipital fissure is similar on both sides. Seen from the mesial 

 surface, it appears to split above into two parts. The posterior one is the true fissure, 

 being continued out into the convexity as above described. The anterior branch just 

 passes the upper l)order of the heniLsphere. The gyrus intercuneatus is made out by 

 separating the parts as far as possible. It is quite hidden, being very deeply placed. 

 Should it rise to the surface, it would separate the internal parieto-occipital fissure 

 from the external, making the former end anteriorly to the latter, as Benhani has 



