OF DRMSON UNIVEkSITV yj 



Of these tracts especially well marked is a bundle of arching 

 fibres passing from this nucleus dorsally toward the nates but apparent- 

 ly converging over the a(|ueduct to the posterior commissure It may 

 be suggested that this nucleus is centre of co-ordination for the orulo- 

 muscular aparatus. 



The region of the thirj itnitriclc. 



Horizontal sections through the lowest j) jrlion of the tuber cine- 

 reum reveal the same struc'.ure as described in llie tu!)er of the alliga- 

 tor, /. <-., a dense layer of epithelium liniig the ventricle, the cells of 

 which give rise to long fibres of connective tissue dividing the space 

 about the ventricle into compartments in which the very numerous 

 flask-shaped cells are closely packed. T.ie entire tuber is filled with 

 these cells. At its posterior portion are two more densely nucleated 

 spots laterad to the lowest point of the fornix tract. 



In higher sections the above-mentioned nuclei and the ceph- 

 alad and caudad j)arts of the fornix tracts become cpiite distinct The 

 nuclei above described, which may be called the j^osterior nuclei 

 of tlie tuber, give rise to fibre tracts passing dorsad and cephalad lat- 

 erally from the cephalad tract of the fornix. About the sides of the 

 third ventricle, cephalad is a large, dense nucleus of small cells, the 

 anterior tuber nucleus, and in front of this on either side, not far cau- 

 dad of the chiasm, is a small tract in cross section. This small bundle 

 can be traced dorsad for some distance, but its ultimate course is un- 

 known. 



The structure about the third ventricle remains (juite constant but 

 cephalad from the lamina terminalis is a nucleus of spider-like, slender 

 multipolar cells with remarkably long and distinct i>rocesses passing 

 in all directions through a coarse reticulum of fibres (Vll b 15). Both 

 divisions of the fornix tract lose their distinct contours before the level 

 of the anterior commissure is reached, the caudad tract, especially, 

 fuses with the gray matter of the thalamus. 'I'he cephalad portion 

 emerges immediately caudad to the commissure. Meynert's bundle 

 at this level is some distance cephalad t.) the oculomotor tracts. 



Three more or less distinct masses of gray matter api)ear in the 

 lateral aspect, the middle one being the largest and most densely nu- 

 cleated and being recognized as the cori)Us geniculatum. 



The most remarkable nucleus remaining is the ganglion of the 

 superior commissure or nucleus of the habenuUv This is a compact 



