306 



ANATOMY OP THE CENTRAL NERYOUS SYSTEM. 



Of the structures named in the figure the small elliptical areas (&), lying 

 between the red nuclei, have not been previously mentioned. The fibers 

 here cut arise in the ganglion habenulas thalami and pass from it downward 

 and backward to a small ganglion, which lies between the cerebral peduncles, 

 the ganglion inter pedunculare. Before entering this ganglion the fibers 

 decussate. The bundle is called the tractus liahenulo-peduncularis, the Fas- 

 ciculus retroflexus, or Meynerfs bundle. Its course is best seen in Fig. 144. 

 In the ganglion habenulse ends the greater part of the taenia thalami, which, 

 as above described, passes up from the lateral portions of the olfactory area. 



The ganglion interpeduneulare was discovered by Gudden and first exactly 

 described by Forel. Gudden showed that after destruction of one ganglion haben- 

 ulae the fasciculus retroflexus of the same side undergoes descending degeneration. 



Fig. 198. — Frontal section through the anterior quadrigeminal bodies of a 

 nine months' fetus, o. <S'., w. 8., upper fillet and lower fillet. Hint. Ldngsb., 

 posterior longitudinal fascicle. 



and that the degenerated fibers may be followed as far as the opposite ganglion 

 interpeduneulare. Ganser disco\'ered another bundle from the tegmentum to the 

 ganglion interpeduneulare. 



The author's investigations on normal dogs and on one in which the habenular 

 ganglion had been destroyed show still further facts: The ganglion interpeduneulare 

 in dogs consists of five different ganglia, in front two pear-shaped bodies lying side 

 by side, covered by a flat plate which lies beside the tegmentum; posteriorly this 

 group is inclosed by a much larger, horseshoe-shaped ganglion, whose posterior 

 portion constitutes the main body, of the ganglion. The slender anterior limbs of 

 this ganglion receive the fibers of the Fasciculus retrofiexus, which lose their med- 

 ullary sheaths immediately after their entrance. In the lizard the Golgl method 

 shows that after decussation they break up into innumerable very fine terminal 



