The brain of Acipenser. 75 
distinct as to structure, central and peripheral relations, and function. 
The one group consists of the centers for the V, VIII, and N. lineae 
lateralis, viz., the nucleus of the spinal V tract, the tuberculum 
acusticum, and the lobus lineae lateralis. The other group is the 
center for the VII, IX and X nerves, viz., the lobus vagi, with the 
secondary vagus tract and its nucleus. The latter tract and nucleus 
lie within the limits of the basal portion of the medulla, but their 
description has been postponed until they could be taken up in con- 
nection with the lobus vagi. 
a) General cutaneous, lateral line and auditory Centers. 
The descending root of the trigeminus, or spinal V. 
— In Acipenser the dorsal tracts of the cord which correspond to 
the funiculi of GoLL and of BurpAcH have their cephalic ending 
in a nucleus which is situated at the junction of the cord and medulla. 
This nucleus is an enlargement of the dorsal horn which stretches 
for some distance cephalad and caudad from the calamus and appears 
in well impregnated transverse sections as a dense mass of inter- 
woven fibres. Sagittal sections are better suited for studying the 
cells and the endings of fibres in the nucleus. The cells measure 
8—20 by 12—48 u. They are ovoid, pyramidal, or irregular and 
have two or more dendrites which present characteristic angular 
bends. The neurites usually pass ventrad, but sometimes cephalad 
or caudad. There are present a very few larger cells, measuring 
16—24 by 52—120 w. 
The fibres of the dorsal funiculi of the cord end by free ar- 
borizations in all parts of this nucleus. Other fibres, which descend 
from the medulla, are found ending by very profuse branches in 
the same nucleus. In transverse sections these fibres together with 
those of the funiculi are seen to cover the nucleus dorsally and 
partly surround it, like a cap. As both structures are traced for- 
ward the nucleus gradually diminishes and, a little cephalad from 
the calamus, gives way to the bundle of medullated fibres which 
continues forward as the spinal V tract, to be described below. The 
descending fibres of the trigeminus and the ascending fibres of 
the funiculi mingle and end alike in all parts of the nucleus, the 
spinal V being, however, the more important. In addition to this 
common nucleus there are a number of cells situated nearer the 
median dorsal raphe, forming an indistinct nucleus which receives 
fibres coming from the VIII and lateral line nerve roots which run 
