The brain of Acipenser. 179 
to the fibres of the secondary vagus tract which run through the 
internal part of the acusticum and the nucleus funiculi to reach the 
lateral tracts. The fibre layer grows smaller caudally and turns 
mesad as a compact bundle to form the commissure. This seems 
to form an abrupt caudal limit to the fibre layer, but upon close 
examination it is seen that a part of the fibres continue caudally 
without crossing. They are very soon lost to view among the cells 
occupying the median dorsal part of the cord. Situated among these 
cells at the mid dorsal line are the giant cells recently described in 
various fishes by FRITSCH, TAGLIANI, SARGENT, and others. These 
cells are in no way related to the fasciculus communis, as I have 
previously (98b) suggested they might be. 
Fig. W. 
In the Amphibia the communis system was described by 
STIEDA (75) in Axolotl and the frog (quoted by Strona, ’95, p. 183) 
and by KÔPPEN (88) in the frog. These authors agree in placing 
the caudal limit of this tract at the point of transition from cord 
to medulla, where it holds a position mesial to the dorsal horns or 
the substantia gelatinosa (imbedded in the gelatinosa, KÖPPEN). 
Osporn ('88) describes two tracts which he calls the fasciculus com- 
munis and fasciculus solitarius. His fasciculus communis is the 
system now under consideration, and the adoption of the name by 
STRONG has led to its general use for the sensory center of the 
19 
