160 THE BRAIN OF THEiTIGER SALAMANDER 



ventricle, and then arborizing in the lateral vestibular area of the 

 auricle (figs. 7, 32, 33; '446, fig. 14). Posteriorly, at the calamus 

 scriptorius, it converges with its opposite fellow, and the two tracts 

 enter, respectively, the medial fascicles of the dorsal funiculi of the 

 spinal cord. Tract a is regarded as a mixed collection of fibers of 

 correlation, related primarily with the lateral-line nerve roots, a 

 supposition which is supported by Kreht's observation ('30, p. 316; 

 '31, p. 422) that in adult Salamandra, in which the lateral-line roots 

 are atrophied, tract a also disappears. It is connected by arcuate 

 fibers with the intermediate and motor zones of both sides, and prob- 

 ably some of these fibers are commissural, connecting the acoustico- 

 lateral areas of the two sides. 



The nucleus of the dorsal funiculi extends for a considerable dis- 

 tance anteriorly and posteriorly of the calamus scriptorius. Fibers 

 of the slender median fascicle of the dorsal funiculus of the cord ter- 

 minate in this nucleus, and some of them continue forward for an 

 undetermined distance in tract a. The nucleus funiculi is connected 

 through tract a with the lateral-line area farther forward by fibers, 

 some of which are probably descending and some ascending. The 

 latter may go as far as the cerebellar primordium in the auricle, 

 though there is no demonstration of this. In Triturus, as described by 

 Larsell ('31, p. 48), unmyelinated fibers descend into tract a from the 

 auricle, thus providing for cerebellar discharge into the lateral-line 

 area. 



Trad h. — This tract is a mixed bundle of myelinated and unmyeli- 

 nated fibers, believed to be related primarily and perhaps specifically 

 with the vestibular roots (figs. 7, 31). The literature contains several 

 descriptions of tract b of Amblystoma ('14a, p. 373; '396, p. 604; 

 '446, p. 317; Larsell, '32) and other urodeles. In the aggregate, these 

 give an incomplete account of it. From the data at hand it is con- 

 cluded that it contains a variety of crossed and uncrossed, ascending 

 and descending, fibers connecting the vestibular areas of both sides 

 with each other, with the underlying tegmentum, with the cerebel- 

 lum, and with the spinal cord. Kreht ('31, p. 423) describes in Proteus 

 a probable connection with the f . longitudinalis medialis. 



Anteriorly, tract h converges with tract a into the vestibular 

 neuropil at the lateral border of the auricle (fig. 91). This is cerebellar 

 territory, the primordium of the flocculus of mammals. Silver im- 

 pregnations show that many of these fibers end in free arborizations 

 in the auricle ('396, figs. 43, 67, 77, 98). This connection is clear in 



