272 THE BRAIN OF THE TIGER SALAMANDER 



f.med.t.), connects with the medial and ventral walls and also has 

 dorsal and ventral components related, respectively, with the dorsal 

 and ventral parts of the hypothalamus. The third group of fascicles 

 comprises the tractus olfacto-peduncularis (tr.ol.ped.), which lies be- 

 tween the lateral and the medial bundles, connecting the anterior 

 olfactory nucleus and the head of the caudate with the hypothala- 

 mus, peduncle, and interpeduncular nucleus. 



Lateral forebrain bundle. — Most of these fibers are connected with 

 the primordial corpus striatum and amygdala, and some of them 

 with the piriform area. The descending fibers correspond with the 

 human ansa lenticularis, and most of them are well myelinated. They 

 appear earlier in ontogeny than do the ascending fibers. The dorsal 

 and ventral fascicles of this bundle interchange fibers and in Necturus 

 are not clearly separable ('336, p. 170). They are connected mainly, 

 though not exclusively, with the dorsal and ventral nuclei, respective- 

 ly, of the corpus striatum, as described in chapter vii. When first 

 studied, this relationship could not be demonstrated ('27, p. 286), 

 but subsequent examination of sagittal sections ('36, p. 335) con- 

 vinces me that this incomplete separation marks the beginning of 

 differentiation of the globus pallidus. In 1927 the ventral fascicles 

 were named tr. strio-peduncularis ('27, p. 287) and the dorsal 

 fascicles tr. strio-tegmentalis, but these terms are inappropriate be- 

 cause both of them terminate in the peduncle and also in the teg- 

 mentum, though in different areas and evidently with different phys- 

 iological import. The dorsal fascicles enter group (9) of the tegmental 

 fascicles and the ventral fascicles enter group (10), as described 

 below. 



The descending fibers of the ventral fascicles {f.lat.t.v. and (10) of 

 the figures) arise from the large cells distributed throughout the 

 striatal gray. Their terminals are widely spread in the ventral parts 

 of the peduncle and isthmic tegmentum. They d6 not extend so far 

 spinal ward as do some fibers of the dorsal fascicles. In the analysis of 

 the tegmental fascicles ('36) these fibers comprise group (10). They 

 make their chief synaptic connections with the large cells of the 

 peduncle and tegmentum, the axons of which enter the ventral teg- 

 mental fascicles of groups (4), (5), and (6), descending to the medulla 

 oblongata, and some of which continue in the f . longitudinalis medialis 

 into the spinal cord. This connection is regarded as provision for 

 cerebral control of mass movements of the trunk, limbs, and eyeballs. 



The descending fibers of the dorsal fascicles (f.lat.t.d. and tegmen- 



