CHAP. XXL] 



OF THE HUMAN BRAIN. 



401 



In a large proportion of brains, and, as it would seem, 

 especially in those of Women, this conformation of the 

 right Occipital Lobe exists to a well-marked extent. In 

 others, it is only slightly marked ; whilst on rare occasions 

 a more or less obvious groove exists on each side. In a 

 still smaller number of cases a groove is met with at 

 the tip of the left instead of the right Occipital Lobe, or 

 it may be absent on both sides.* 



The Occipital Convolutions in the situation of the 

 groove are distinctly depressed, but no projection from the 

 inner surface of the skull or thickening of the membranes 

 has ever been met with which could account for its forma- 

 tion. Of late the writer has adopted the view that this 

 ' occipital groove ' is due to the pressure exerted by the 

 posterior extremity of the longitudinal sinus and the right 

 side of the 'torcular Herophili ' or meeting-point of the 

 venous sinuses (fig. 148). Why the pressure should be more 



* In thirty-five consecutive post-mortem examinations the con- 

 dition of the Occipital Lobes has been noted, partly by myself and 

 partly by Mr. J. T. Gadsby or Mr. C. E. Beevor my late able 

 'assistants' at University College Hospital-- -with the view of 

 ascertaining the relative frequency of these different conditions. 

 The results are embodied in the following Tables: 



TABLE I. 



Side. 



Sex. 



M. P. 



Right . . 15 13 

 Left. ..11 

 Both Sides 3 1 

 Absent. - 1 0. 



20 15 



In Table II. under ' Degree,' the figure 3 signifies that the 

 groove was * very well marked'; 2, that it was ' moderately well 

 marked ' ; and 1, that it was only * slightly marked.' 



D D 



