X Proceedings of the Association of American Anatomists 



The outline of the lateral surface resembles closely that of the mesal 

 surface, as seen in medisections of the diacoele. But its plane is at such 

 an angle (dorsiventral) to that of the mesal surface as to make the area 

 of the dorsal surface almost three times greater than that of the ventral 

 surface. The entire lateral surface is in relation with the internal cap- 

 sule of the hemisphere. 



The mesal surface is the wall of the diacoele. Its ventral border, 

 cephalad, joins the ventral extremity of the cephalic border of the thala- 

 mus at an angle situated just laterad to the apex of the tuber or where 

 the infundibulum descends. 



The pulvinar is a curved (convexity caudad) four-sided area connect- 

 ing dorsal and ventral surfaces. The dorsal boundary, the same as the 

 caudal border ("base") of the triangular dorsal surface, is much longer 

 ento-ectally than its ventral boundary, i. e. the caudal border ("base") 

 of the triangular ventral surface, because of the angle — already men- 

 tioned — of the plane of the lateral surface to that of the mesal surface. 



For the same reason, the plane of the lateral boundary of the pulvinar 

 converges dorsiventrad to that of the mesal boundary; while these boun- 

 daries themselves are curved (like the pulvinar), each one uniting (cau- 

 dad) the following borders between surfaces of the thalamus: the lat- 

 eral one, the border between dorsal and lateral surfaces with that be- 

 tween lateral and ventral surfaces ; and the mesal one, the border between 

 dorsal and mesal surfaces with that between mesal and ventral surfaces. 

 Laterad to the lateral boundary of the pulvinar extends a process of thala- 

 mus into the ecto (prse) geniculum. 



The dorsal surface of the thalamus, caudad, curves into the pulvinar. 

 Cephalad, this surface presents the " anterior tubercle," laterad and 

 mesad to which are the borders between respectively the lateral and dor- 

 sal surfaces, and the dorsal and mesal surfaces; while cephaloventrad to 

 which, these borders unite into the cephalic border of the thalamus. 



The ventral surface of the thalamus, narrow, triangular and concave 

 ventrad, has for its " base " or caudal border the ventral boundary of 

 the pulvinar. It presents, caudo-cephalad, three areas: (1) The caudal, 

 practically the ento (post) geniculum. (2) The medial, entirely occupied 

 by tegmental fibers. (3) The cephalic, which is that portion of gray 

 matter commonly included in the " tuber cinereum." More exactly, it 

 is the lateral area of the so-called " tuber cinereum," the mesal area of 

 which, the tuber, is part of the floor of the diacoele and is continuous 

 dorsad with the terma. This lateral area of the " tuber cinereum," or 

 cephalic area of the ventral surface of the thalamus, has been observed 



