72 W. BLAXLAND BENHAM. 



is well developed. Posteriorly it is continuous with the prse- 

 centralis inferior, whence it runs nearly directly forwards for 

 some distance and then bends downwards in front of the orbito- 

 frontalis (e. o.), when it divides into a fore-and-aft nearly hori- 

 zontal fissure {w.), and can be traced forwards to the frontal 

 pole. The anterior branch appears to be the fronto-marginalis 

 of Wernicke. 



In his description of this fissure in man, Cunningham states 

 that the hinder limb of the fork lies between the two anterior 

 limbs of the Sylvian fissure. Granting that the s. frontalis 

 inferior is identical in man and apes, — and in " Sally " it closely 

 resembles the arrangement figured by Cunningham on p. 248 

 for man, — the hinder branch of the fork ought to have the 

 same relation to the fronto- orbital furrow {e. o.) as it has in 

 man to the anterior horizontal limb of the Sylvian fissure, if 

 Cunningham's identification of the fronto-orbitalis is the true 

 one. But here in '' Sally " it has not this position ; a fact 

 which is adverse to Cunningham's interpretation of these other 

 furrows. But in other chimpanzees this fissure marked " w." is 

 not related to the ^^ s. front, inferior," but to the '^medius," 

 as in fig. 35, where the s. frontalis inferior is short and its 

 anterior end is surrounded by a curved fissure — part of the 

 " medius " (/. m.) — which passes downwards and divides near 

 the orbital surface of the brain into a fore-and-aft horizontal 

 furrow (w.), which can be traced round to the frontal pole. 

 This appears to be the s. fronto-marginalis of Wernicke, 

 and this brain resembles in this respect the one figured by 

 Cunningham (fig. 68, p. 290). In other cases the "medius" 

 runs in the same direction, but does not divide (fig. 38). 



The s. frontalis medius in " Sally" is unconnected with 

 the s. prsecentralis inferior, and is quite a distinct fissure on 

 both hemispheres. 



Turning now to the left side of "^ Sally's" brain (figs. 10, 13), 

 we find the sulcus prsecentralis inferior {p. c. i.) is a well-marked 

 continuous furrow extending from nearly the Sylvian fissure 

 upwards for about half the surface of the hemisphere. There 

 appears to be no ramus horizontalis, unless it is represented by 



