26 Dr. Foville on the Anatomy of the Brain. 



of the crus cerebri like a kind of bracelet, others separating 

 from it in the greater part of their course, but always coming 

 back to unite at their termination with the white quadrangle 

 of the fissure of Sylvius. 



Setting off from the crus, the first of these parts is the white 

 superficial covering of the optic thalamus, the fibres of which 

 are circular. 



The second is the taenia semicircularis, incomplete as a 

 ring when considered alone, but completed by the quadrangle 

 with which it directly unites in front, whilst behind it joins the 

 great tuberosity of the convolution of the cornu ammonis, 

 attached to the external part of the superficial quadrangle. 



Thirdly, the corpus striatum itself forms by its gray matter 

 alone a complete circle, or rather an ellipse, the inferior ex- 

 tra-ventricular part of which is covered by the quadrangle so 

 often mentioned. 



Fourthly, to the outer side of the corpus striatum there is a 

 fibrous circle, which surrounds it as the taenia semicircularis 

 compasses the optic thalamus. So far as I know, this fi- 

 brous ring has not hitherto been described. 



Fifthly, the corpus fimbriatum and the corresponding half 

 of the fornix form likewise a complete circle with the fibrous 

 layer of the fissure of Sylvius. In the sixth place would 

 come, if we had not before described it, the white band of the 

 border. 



In the seventh and last place, the two little bands situated 

 upon the corpus callosum close to the median line, termi- 

 nate, like all the preceding parts, at the anterior and pos- 

 terior limits of the white perforated surface internal to the 

 fissure of Sylvius. 



The corpus callosum itself is in intimate relation with all 

 these concentric circles. Its particular disposition was de- 

 scribed in a memoir which I had the honour of reading be- 

 fore the Academy of Medicine at Paris in 1825; but the death 

 of Beclard, who was appointed to report on my paper, de- 

 prived me of the judgement which that illustrious professor 

 would have formed. 



There is not, I believe, any communication between the 

 fibrous expansions of the inferior part of the crura of the op- 

 posite sides of the brain. 



It appears to me that in man the anterior commissure only 

 unites those parts of the opposite sides which are connected 

 with the nerves of sensation. The well-known fact that in 

 many mammifera this commissure only stands on each side 

 to the olfactory nerves instead of reaching from one hemi- 

 sphere to the other, adds force to the opinion I express, that 



