1880. J NATURAL SCIENCES OF PHILADELPHIA. Ill 



H3'lol)ates and Ateles almost to the same extent as in the Orang, 

 but it is more developed in the latter than in the Chimpanzee. It 

 is called also the "premier plis de passage externe," by Gratiolet, 

 the " obere innere Scheitelbogen-Windung,'' by Bischott", the •' lirst 

 annectant gyrus,"' X)y Huxley, and " first bridging convolution," 

 by Turner. The second occipital convolution connects the occipital 

 lobe with the angular gyrus. In my Orang it was partl}^ concealed 

 bj- the first occipital. It was not as superficial as in man. The 

 third occipital gj'rus is continuous with that part of tlie temporal 

 lobe below the first temporal fissure. I noticed, also, in my 

 Orang the " quatrieme plis de passage "" of Gratiolet. On the 

 mesial side of the occipital lobe in n\y Orang, was well seen the 

 " deuxieme 'plis de passage interne" of Gratiolet, the " untere 

 innere Scheitelbogen-Windung " of BischofF, which separates the 

 ealcarine from the parieto-occipital fissure ; and in both the 

 Orang and Chimpanzee, more especially on the left side, I had no 

 difficult}' in recognizing the " premier plis de passage interne '' of 

 Gratiolet, its convexity turning inwards, while that of the first 

 occipital gyrus, or the " premier plis de passage externe," turns 

 outward. These two convolutions, the first occipital gyrus and 

 the " premier plis de passage interne," in my Orang were con- 

 tinuous. They are regarded as one by Bischott', forming his 

 " obere innere Scheitelbogen-Windung," but as two b}^ Gratiolet, 

 constituting his " premier plis de passage externe et interne." 



The temporal lobe in the Orang is much less convoluted than in 

 man, or even in the Chimpanzee. Tlie first temporal fissure and 

 first temporal convolution are well marked, but the second and 

 third are badly defined. The fusiform and lingual lobes are sep- 

 arated b}" the inferior occipito-temporal fissures, the collateral 

 fissures of Huxley. The island of Reil was perfectly covered in 

 both the Chimpanzee and the Orang by the operculum, but was 

 not convoluted in my Orang. The surface in places was slightl}- 

 roughened. I noticed, however, three or four convolutions in 

 the Chimpanzee. On making a section of the left hemisphere of 

 the Orang I noticed that the corpus callosum was relativeh^ 

 smaller than in man, but that the ventricle exhibited an anterior, 

 middle and posterior cornu, the corpus striatum, trenia semi- 

 circularis, thalamus opticus and fornix were well developed, the 

 hippocampus major with corpus fimbriatum were perfectly evident, 

 and the hippocampus minor larger relatively than in man. I did 



