GANGLION AR GRAY MATTER. 211 



internal medullary lamina separates it from the other nuclei of 

 the same thalamus. It gives origin to a part of the ventral stalk 

 of the thalamus. According to Bechterew it probably gives 

 rise to some descending fibers that run down the cord. (Jas. S. 

 Collier has traced thalamo-spinal fibers in the cat down the lateral 

 column of the cord.) 



(2) The lateral nucleus is the largest. It extends from superior 

 to inferior surface the entire length of the thalamus, and includes 

 the center median (Luysi) and the arcuate nucleus, both of which 

 fuse with it posteriorly. It also fuses with the nucleus of the 

 pulvinar. It forms the terminal nucleus for the larger part of 

 the tegmental fibers, especially of the medial fillet, the spino-thala- 

 mic tract, a part of the medial longitudinal bundle and the brach- 

 ium conjunctivum of the cerebellum; and it constitutes the nucleus 

 of origin for most of the fibers of the cortical fillet. Destruction 

 of this nucleus interrupts the common sensory path, and causes 

 anesthesia and ataxia of the opposite side. 



(3) The nucleus of the anterior tubercle (Fig. 44) receives the 

 fasciculus thalamo-mammillaris (Vicq d'Azyri) from the corpus 

 mammillare and is thus connected with the columna of the for- 

 nix (Fig. 66). 



(4) The nucleus of the pulvinar (Fig. 44) is an important one. 

 It receives about twenty per cent, of the optic fibers and gives 

 rise to a corresponding number of the corticipetal fibers in the 

 optic, or occipito-thalamic radiation ; hence, a lesion of the pulvinar 

 impairs vision. It is continuous with the lateral nucleus. 



(5) The nucleus of the habenula belongs to the epithalamus 

 (Fig. 64). It lies beneath the trigonum habenulae. It receives 

 fibers from the rhinencephalon through the medullary stria of 

 the thalamus, and originates a bundle of fibers, the fasciculus 

 retroflexus (Meynerti), which may be traced back through the 

 tegmentum to the interpeduncular ganglion in the substantia 

 nigra. Beyond this, connections are probably established with 

 the motor nuclei of cerebral nerves. 



The white matter of the thalamus includes, first, the stratum 

 zonale of the superior surface, which is derived from the occipito- 

 thalamic radiation and the lateral root of the optic tract; and, 



