MORPHOLOGY OF THE CEREBRAL CONVOLUTIONS. 297 



fissure extends to some distance above the posterior end of the Sylvian. A similar 

 condition to this is described by Gratiolet as occurring sometimes in the brain of 

 Cercopithecus sabaeus. I have also found this occurring in brains of Macacus 

 cynomolgus, M. nemestrinus, Plate XXXVII, figs. 1, 2, 8 and 9. The fissure, o. t 2 , 

 represents the second inferior occipitotemporal fissure. It is the middle temporal 

 of Ecker and some other writers, the postero-temporal of Huxley. It is not as 

 strongly marked as the first and it varies greatly in different individuals. These 

 two fissures mark out and separate quite distinctly three laterally situated occipito- 

 temporal convolutions the most inferior of which extends inwardly to form a large 

 portion of the infero-mesial surface. 



The superior occipi to-temporal convolution, S. O.T., O.T 1 , the superior temporal 

 of Huschke and most others, gyrus temporalis primus of Wagner and the antero- 

 temporal of Huxley, is the best defined and most constant of the lateral convolu- 

 tions of the occipito-temporal lobe. It is contained between the Sylvian and superior 

 occipito-temporal fissures and extends from the anterior extremity of the temporal 

 lobe backward to join the inferior parietal gyrus, P 2 P 2 arching around the 

 posterior extremity of the fissura Sylvii. I have found this convolution simpler in 

 the negro brain, that is, possessing fewer secondary markings, than in the white. 

 It is also narrower, Plate XLI, fig. 1, Plate XLII, fig. 1, approaching in this respect 

 the condition as found in the chimpanzee, etc., Plate XXXIX, fig. 4. 



The middle occipito-temporal convolution, M. 0. T, gyrus occipito-temporalis 

 meclius, lies directly below the superior, separated from it by, s. o. t', and bounded 

 below by the inferior-occipito temporal fissure, i. o. t 2 . It extends from the 

 anterior extremity of the temporal lobe backward to the occipital. 



The third occipito-temporal convolution, I.O.T. 3 gyrus temporalis inferior, lies 

 directly below the middle and extends inwardly, so as to appear upon the mesial 

 surface. It, like the two preceding, extends from the occipital to the anterior ex- 

 tremity of the occipito-temporal lobe. 



Mesial Occipito-temporal and Occipitofrontal Surfaces and their Relation to Each 



Other and to the Occipital Lobe. 



The mesial surface is separated by the fissura tri-radiatus into three divisions: 



1. A posterior marked off by the internal extremities of the primary occipital 

 arch, 01 and 02, fig. 8, which forms the mesial portion of the occipital lobe. 



2. A mesial occipito-temporal below, rightly recognized by Gratiolet, Ecker 

 and others, situated beneath the calcarine and inferior branch of the mesial arched, 



the hippocampal fissure, fig. 8. 



3. A portion above the calcarine and upper branch of the mesial arched, the 

 callosal fissure, which so evidently corresponds in its relations and structure to the 

 preceding that I propose to designate it as the mesial occipito-frontal surface of an 

 occipito-frontal lobe. This mesial occipito-frontal, M.O.F., fig. 8, represents the 

 combined mesial surface of the parietal and frontal lobes of Ecker and others, the 

 fronto-parietal of Gratiolet and the French authorities. Good reasons for this 



