438 PHYSIOLOGICAL SERIES. 



quite independent of the great vertical sulcus (so peculiar 

 to thB Orang), which I am inclined to regard as a separate 

 posterior element of the " rectus," in spite of the fact that 

 in most brains of Simla it is joined not to the straight but 

 to the arcuate sulcus. 



The arcus occipitalis is wholly submerged on both sides. 



After studying a series of intermediate forms, I am 

 persuaded to regard that sulcus, which we would unhesi- 

 tatingly call "inferior occipital" if we compared this 

 specimen directly with a Macaque's brain, as the occipito- 

 temporal, which has become so deepened at the expense of 

 the inferior occipital, that the latter has become reduced to 

 an altogether insignificant furrow. 



The shape of the corpus callosum and septum lucidum 

 are most admirably demonstrated. 



Presented by Professor John Marshall. 



D. 653. The brain of a small Orang-Outang (Simla morio). 

 The left hemisphere has been detached. 



In this alone of all the Orang-brains the posterior cud of 

 the Sylvian fissure is not bifurcated. Here again tlio 

 arcuate sulcus and posterior element of the "rectus" 

 present that peculiar relationship, which seems to be so 

 characteristic of the Orangs (compare D. 651 and D. 649). 

 And in the right hemisphere again the arcuate sulcus is pro- 

 longed into the position of the superior frontal, and is also 

 superficially linked to the Sylvian fissure by the inferior 

 transverse sulcus (Cunningham calls it " diagonal " in the 

 case of the Orang ; Mem. Roy. Irish Acad. 1890, p. 2! -1), 

 as in the corresponding hemisphere of D. 651. 



The union of orbital and inferior frontal (rectus) sulci is 

 again found here in both hemispheres. 



The calcarine sulcus is unl>ranched, as in Alnnntfa and 

 Ateles, but some of the postcalcarine elements exist as 

 independent sulci. 



The arcus occipitalis is wholly uncovered on the left, and 

 almost completely hidden by the occipital operculum on the 

 right hemisphere. 



Although the general appearance of the anterior insular 



