1903.] The Retrocalearine Region of the Cortex Cerebri, 



59 



" The Morpholep of the Eetrocalcarine Eegion of the Cortex 

 Cerebri." By G. Elliot Smith. M.A., M.D., Fellow of St. 

 John's College, Cambridge, Professor of Anatomy, Egyptian 

 Government School of Medicine, Cairo. Communicated by 

 Professor A. Macalister, F.B.S. Received December 1, 

 1903 —Read January 28, 1904. 



Although many writers, amongst whom Henschen, Vialet and 

 Ramon y Cajal may he specially mentioned, have devoted a con- 

 siderable amount of attention to the study of the white streak in the 

 occipital cortex cerebri, which Gennari first described in 1776 as 

 "lineola albidior admodum eleganter," iw one, so far as I am aware, 

 has ever used this feature as a guide to the identification of homologous 

 areas and sulci in different brains. On the contrary, it has been 

 employed as evidence that the furrows on the surface of the hemi- 

 sphere have no value for the orientation of physiological areas, seeing 

 that it occupies the edges of two adjoining gyri and the floor of 

 the sulcus between them.* In this preliminary note I hope to 

 demonstrate that Gennari's stria is a sure criterion for the identifica- 

 tion of three or perhaps four sulci. I began the study of its distribu- 

 tion in the brain of Man and that of the Apes to test the accuracy of 

 the homology which I had suggested between the sulcus occipitalis 

 lunatus (mihi) in the former and the so-called " Affenspalte " of the 

 latter, f In the course of these investigations I found that the 

 stria-bearing cortex (or "&rea striata occipitalis," as it may be called) 

 presented such definite relations to the calcarine sulcus in the Human 

 brain, that it could be used as a ready and sure means of determining 

 the homologue of this furrow in the Apes and the other Mammalia. 



The accompanying diagram of the mesial surface of the right 

 occipital region of the brain of an adult male Egyptian Fellah will 

 make this relationship clear. The drawing is schematic in as much as 

 all the submerged gyri are represented as though they were exposed 

 on the surface ; the distribution of the stria Gennari is shown b}^ the 

 punctate shading. 



The furrow commonly known as the "fissura calcarina" consisted, 

 in this case, of four separate elements, of which the most anterior one 

 alone was strictly entitled to Huxley's term " sulcus calcarinus." The 

 other three furrows (r l , r' 2 and r 3 ) represent the sulcus for which in a 



* Oscar Vogt, " Zur anatomischen Grliederuag cles Cortex Cerebri," 'Journal f. 

 Psychologie und Neurologie,' vol. 2, part 4, 1903, p. 168 ; see especially Plate 11, 

 fig. 1. 



f " The so-called ' Affenspalte ' in the Human (Egyptian) Brain," ' Anatomischer 

 Anzeiger,' 1903, pp. 74-83. 



