THE TEGMENTUM OF THE CRUS CEREBRI AND ITS GANGLIA. 437 



Fig. 249. 



Fig. 249. Transparent transverse section from the ganglia of origin 

 of the optic tract of Man. M, The medulla of the cerebral lobes ; u, 

 the tractus options ; Bk, red nucleus of the tegmentum ; Nc, nucleus 

 caudatus ; 8t, stria cornea ; Th, pulvinar ; Qu, superior corpus quadri- 

 geminum ; Gi, corpus geniculatum internum ; G-e, corpus geniculatum 

 externum ; S, substantia nigra ; A , aquseductus ; A', grey matter of 

 the central cavities around the aquaeduct ; R, the median raphe of 

 the tegmentum ; La, lamina perf orata posterior ; R, converging 

 radiations into the pulvinar ; Bs t the brachium of the upper corpus 

 quadrigeminum ; Bi, the brachium of the inferior corpus quadri- 

 geminum, from which the lowermost fasciculi of the internal corpus 

 geniculatum run into the tractus opticus ; W t optic root of the upper 

 corpus quadrigeminum (through the intermediation of the internal 

 corpus geniculatum) ; Xp, decussation in the roof of the aquaeduct, 

 through which the right arm of the superior corpus quadrigeminum 

 is conducted into the loop layer of the tegmentum, Tl ; Xd, decussa- 

 tion in front of the aquaeduct, which is part of the interlacement of 

 the tegmentum, To, formed by fibres proceeding from the fifth nerve, 

 V ; in', roots of the oculo-motor nerve ; T, spinal-cord fasciculi of 

 the tegmentum ; V, transverse section of the descending root of the 

 fifth with the adjoining vesicular cells ; L, posterior longitudinal 

 fasciculi ; in, nucleus of the nervi oculomotorius and trochlearis ; 

 P, fasciculi of the crus cerebri entering the above-named nucleus as 

 the fibrse rectae of the raphe', R. 



