CHAP. XXIII.] OF THE HUMAN BRAIN. 443 



seeing that they are so mixed up as not to be traceable 

 separately; and it is not quite what might have been 

 expected." At certain parts, however, as Broadbent 

 points out, a triple if not a quadruple mode of supply is 

 easily shown, and in illustration he cites the following 

 facts * : 



The fibres which pass to the tip of the Occipital Lobe from 

 three of these sources, viz., Corpus Striatum, Thalamus, and Cor- 

 pus Callosu.rn, form distinct masses at their point of departure, 

 and only blend with one another near their termination in the 

 Convolutions. 



A similarly-independent communication exists with certain 

 Convolutions so situated, that in order to reach them fibres ot 

 one or other of the three orders in question, have to take an extra- 

 ordinary course. Thus, the Convolutions of the anterior extremity 

 and of the upper margin of the Temporal Lobe, are directly 

 connected with (1) the adjacent Corpus Striatum, by fibres which 

 stretch across the fissure of Sylvius ; (2) the fibres of the Thala- 

 mus, to the same convolutions, are given off from that part of it 

 which bends round in the roof the descending cornu of the ven- 

 tricle, whence these afferent fibres diffuse themselves so as to reach 

 the Convolutions in the regions specified; whilst (3) the ' commis- 

 sural ' fibres for these same parts are chiefly represented by those 

 of the Anterior Commissure, which from a functional point of 

 view, is to be regarded as a detached portion of the great trans- 

 verse commissure or Corpus Callosum. The ' commissural ' fibres 

 are, however, also represented by certain anterior fibres of the 

 Corpus Callosum itself, which, near the anterior perforated space, 

 cross to the apex of the Temporal Lobe. 



Even more extraordinary is the separate course taken by those 

 of the three sets of fibres to which we are referring that happen 

 to be in relation with the Hippocampus Major. This structure, 

 Broadbent says, "is in communication with the Corpus Striatum, 

 at its uncinate extremity ; with its fellow in the opposite hemi- 

 sphere by the reflected part of the splenium corporis callosi, 

 which I have called the commissure of the hippocampi ; f but its 



* Loc. cit. p. 433. 



f Corresponding with the * psalterial fibres ' already referred to 

 in a previous chapter (pp. 273, 274). 



