372 C. JUDSON HERRICK 



ventro-laterally into relation with the spinal V root, some, how- 

 ever, reaching the fasciculus solitarius, the VIII root, the ascend- 

 ing secondary visceral tract, the spino-bulbar tract and the motor 

 tegmentum. The predominant physiological characteristic of 

 these neurones is probably determined by their connection with 

 the spinal V root; i.e., they are comparable with those of the mam- 

 malian substantia gelatinosa Rolandi. Nevertheless it is evident 

 that they are not exclusively devoted to this function. A single 

 neurone of this sort is seen also in figure 41 and two others in 

 figure 39, the latter figure illustrating also the mode of termina- 

 tion of the visceral sensory vagus root fibers. Figure 38 shows a 

 single neurone, some of whose dendrites arborize in the fascic- 

 ulus solitarius and some in the spinal V root. The axon is appa- 

 rently directed into the ascending secondary visceral tract. In 

 several cases I have seen similar axones dividing, one branch 

 entering the ascending secondary visceral tract of the same side, 

 the other crossing in the ventral commissure to the other side. 



Figure 39 on the left side shows the dendrite of a neurone lying 

 among those which we have above compared with the substantia 

 gelatinosa Rolandi entering the fasciculus solitarius. The axon 

 of this neurone can be followed across the ventral commissure 

 and into the tractus bulbo-tectalis of the opposite side. In Golgi, 

 Cajal and Weigert preparations of both larvae and adults the 

 tractus bulbo-tectalis is seen to be made up of similar fibers from 

 the most ventral part of the ventral commissure. This tract 

 can be followed caudad as far as the bulbar lemniscus (see fig. 

 16), viz., as far as the caudal end of the area acustico-lateralis. 

 Reading the sections forward from this level, the tractus bulbo- 

 tectalis increases in size and follows closely the ventral border 

 of the bulbar lemniscus into the tectum mesencephali (figs. 4 to 

 16) , its fibers being smaller and in the adult less heavily myelinated 

 than those of the lemniscus. It enters the tectum superficially of 

 the lemniscus (figs. 4 to 6) and in the caudal part of the midbrain 

 it ascends rapidly to a position dorsally of the lemniscus, where its 

 fibers immediately terminate in free arborizations among the 

 dendrites of the nucleus posterior tecti, which are directed forward 

 to meet them. My evidence as to the location of the cells from 



