578 ON A COMPLETE DEBOUCIIEMENT OF THE SULCUS ROLANDO, 



ON A COMPLETE DEBOUCHEMENT OF THE SULCUS 

 ROLANDO INTO THE FISSURA SYLVII IN SOME 

 BRAINS OF AUSTRALIAN ABORIGINALS. 



By N. de Miklouho-Maclay. 



(Plate 18.) 



One of the most characteristic of the Sulci o^ the human brain, 

 as well as one of the first [recognisable at the end of the fifth 

 month] is, as we know, the Sulcus Rolando. 



By reason of the constancy of the presence of this Sulcus in the 

 human brain, the variations of the same appear to me the more 

 important. A complete junction of the Sulcus Rolando with the 

 Fissura Sylvii is very rare in the brains of our race, though a case 

 of this variation has been described by Turner. Prof. D. Zeruoff, 

 who has studied the individual types of the Sulci in the human 

 brain and has published a very interesting and useful work (1) about 

 the subject, has carefully examined the Sulci of not less than 100 

 brains, which have served him as mater ialfor this work, does 

 not mention one case of this variation (2). Prof. A. Ecker in his 

 work about the Convolutions of the human brain (3) says : — A 



(1 ). Individual Types of the Sulci in the human brain. By D. Zernoff, 

 Professor of Anatomy of the University of Moskow. With 74 woodcuts. 

 Moskow 1S77, (in Russian). 



(2) Prof. Zernoff says : — " About their (the Sulci in general), constancy 

 " and variation of shape there exists in the literature very different accounts. 

 "But all agree, that Fis. Rolando and the Ram. Ascendens fis. Sylvii are 

 " absolutely constant and their individual variations are insignificant. . . . 

 •■ As regards variableness in the position and outlines the fis. Rolando is the 

 "least susceptihle. All its individual peculiarities are limited to small 

 "variations in the position of the upper end. sometimes a little further 

 "forward, sometimes further back. Its lower end approaches more or less 

 '• the horizontal ramus of the fis. Sylvii." (Loc. cit , p. 11.) 



(3). On the Convolutions of the human brain. By Dr. A. Ecker, Professor 

 of Anatomy and Comparative Anatomy in the University of Freiburg, Baden. 

 Translated by John C. Galton, M.A. Oxon., M.E C.S., F.L.S. London, 1873. 



