74 W. BLAXLAND BENHAM. 



association of furrows occurs, somewhat like that in fig. 35. 

 The ramus horizontalis is connected, as usual, with the s. 

 prsecentralis inferior. The s. frontalis medius is a curved 

 fissure, concave downwards, lying some little distance in front 

 of the prsecentralis inferior; from this is given off* a branch 

 which runs forward — a modification of the ordinary forking 

 of this fissure. But where is the " inferior " ? 



Just below the medius and lying parallel to the ramus hori- 

 zontalis is a very short fissure (separated from the prsecentralis 

 inferior by a gyrus, which just reaches the surface), crossing 

 the top of a vertical fissure of considerable extent. This latter 

 passes downwards nearly to the anterior limb of Sylvius. 

 This fissure appears to represent the sulcus diagonalis, and 

 the horizontal one at its upper end the s. frontalis inferior. 

 We have in this chimpanzee brain a condition resembling the 

 foetal human brain of eight months figured on p. 250 by 

 Cunningham — the " inferior," however, being shorter in the 

 chimpanzee. 



The brain represented by fig. 38 is of interest in that the 

 s. frontalis secundus is divided into two pieces by a broad 

 gyrus, one portion remaining continuous with the prsecentralis 

 inferior — a condition resembling that of a seventh month 

 human foetus figured by Cunningham on p. 276, fig. 63 ; and 

 it is probable that the part of the curved longitudinal fissure 

 in fig. 33, labelled ? f^., is a similarly disjointed portion of 

 the " frontalis secundus." 



It is unnecessary to enter into further detail, as an examina- 

 tion of the figures will show the interpretations which I put 

 upon the various fissures. 



10. Results of the Comparison of a Series of Chimpanzee 



Brains. 

 1. The parieto-occipital fissure, originally a simple and 

 single incision on the mesiad side of hemisphere, frequently in 

 the chimpanzee and more rarely in man becomes divided into 

 two fissures by the gyrus intercuneatus becoming superficial. 

 Of these two portions, the superior, or lateral parieto-occipital, 



