326 MORPHOLOGY OF THE CEREBRAL CONVOLUTIONS. 



parietalis inferior, and also merging into the middle occipito-temporal convolution, 

 M.O.T, as can be seen in Plate XXXVII, figs. 1, 2, 8, and 9; Plate XXXVIII, figs. 

 4 and 11, in the monkeys marked 4 ; in the Chimpanzee, fig. 13, Plate XXXVIII, 

 x, and in Man, fig. 1, Plate XLII; fig. 1, Plate XLIV ; figs. 1, 3 and 4, Plate XLI, 

 and figs. 1 and 2, Plate XLIII, x. It forms the troisieme pli de passage exttrne 

 of Gratiolet. 



Before passing to the consideration of the morphological type or plan of the 

 occipital lobe as I consider it, it will be necessary to examine the views and nomen- 

 clature of previous observers. Ecker distinguishes on the lateral surface of the 

 occipital lobe, another fissure or fissures, besides the fissura occipitalis transversa, 

 \ which he calls the fissure or fissura? occipitales longitudinales. These fissures, 

 together with the transversa, mark off, according to Ecker, three occipital con- 

 volutions. The first one he places above the transverse fissure and calls it the 

 gyrus occipitalis primus. It includes the erste obere Hinterlappenwindung of 

 Wagner ; the pli de passage superieur exteme + the pli occipital sttperieur of 

 Gratiolet; obere innere Scheitelbogenwindiing of Bischoff, first external annectant 

 gyrus of Huxley, first bridging annectant or connecting gyrus of Turner, par- 

 occipital of Wilder ; the concealed convulsion, 2, (see plates) of the monkeys and 

 apes. 



The second convolution he calls the gyrus occipitalis secundus. This is 

 included between the transverse occipital and the longitudinal. It represents the 

 pli occipital moyen + the deuxieme pli de passage exteme of Gratiolet ; the 

 zweite mittlere Hinterlappenwindung of Wagner, gyrus medius of Pansch, medio- 

 occipital and second external annectant gyrus of Huxley. 



The third or lower occipital convolution Ecker calls the gyrus occipitalis 

 tertius. It represents the pli occipital infer ieur + the quatrihne pli de passage 

 exteme; the dritte untere Hinterlappenwindung of Wagner, gyrus occipitalis inferior 

 of Pansch. With this division of the occipital lobe I cannot agree. In the first 

 place, the gyrus occipitalis primus ought not to be considered, it appears to me, as a 

 distinctly separate part of the occipital lobe at all. We have seen how in the 

 monkeys the fissure O l marks off clearly the occipital lobe from the rest of the 

 hemisphere. Now, the convolution which Ecker and others have called the first 

 occipital convolution (gyrus paroccipitalis. Wilder) develops as we have seen from 

 the floor of this occipital cleft, O 1 , anteriorly to the proper boundaries of the occipital 

 lobe, and it must, therefore, give rise to confusion to place it in the latter. Before 

 reaching the surface, before interrupting the continuity of the fissure, O 1 , and whilst 

 lying concealed in the depths of this fissure, it certainly does not belong to the occipi- 

 tal lobe. Why then should it be considered a part of it when it merely reaches the 

 surface in the higher apes and Man ? This late developing gyrus is really only an 

 increased extension and evolution of the gyrus parietalis superior, as may be seen 

 by examining the various plates in which it is shown developed, as in the Chim- 

 panzee, Plate XXXVIII, fig. 13, and in Man, Plate XXXVI, figs. 5 and 6. 

 Huschke appears to be the only one who regards it in this light. He calls this 



