322 Jouninl of Comparative Neurology and Psychology. 



Fig. 6. Section taken through the caudal end of the second lobe, including a portion of the dorsal 

 and ventral roots of the second spinal nerve. The dorso-lateral fasciculus at this level is composed 

 partly of root fibers and partly of massive secondary tactile tracts between the second and third lobes. 

 Secondary tactile tracts pass from the grey matter of the lobe to this fasciculus and to the ventral cornu 

 and fasciculi proprii adjacent. 



Fig. 7. Section through the cephalic end of the second lobe, showing overlapping first lobe and the 

 caudal end of the somatic commissural nucleus (comm. nuc.) and contained dorsal commissure, which 

 from this point toward the head may be termed the somatic commissura infima. 



Fig. 8. Section .225 mm. farther toward the head through the somatic commissural nucleus {comm. 

 nuc). This nucleus is divided into dorsal and ventral parts, each with a fascicle of medullated commis- 

 sural fibers. .A vestige of the second accessory lobe surrounded by medullated secondary tactile fibers 

 (cf. Fig. 9) is embedded in the substance of the first lobe. 



Fig. 9. Section .221; mm. farther toward the head, showing dorsal and ventral portions of the somatic 

 commissural nucleus and their commissures (designated com. inf. d. and com. inf. v., respectively). 

 The more dorsal fibers, designated sec. t. tr., are secondary tactile tracts from the cephalic end of the 

 second accessory lobe (cf. Fig. 8); the more ventral ones are short tracts of similar character passing 

 between the first and second lobes (fasciculi proprii). 



Fig. 10. Section through the cephalic end of the first lobe and somatic commissural nucleus, the 

 latter still showing the division into dorsal and ventral portions. The spinal V tract occupies the dorsal 

 part of the section and is sending terminal filaments into the first lobe, which thus serves as nucleus 

 spinal V as well as dorsal cornu for the first spinal nerve (cf. Fig. 9). The nucleus funiculi appears at 

 this level and receives terminals of the dorso-lateral fasciculus, embedded within whose fibers it lies. 

 Large secondary tactile tracts spring from the funicular nucleus and cross in the ventral commissure 

 {sec. t. ir. cruc), terminating mainly in the adjacent ventral cornu. Some turn caudad in the ventral 

 funiculi, and probably a smaller number join the tractus spino-tectalis {ir. sp. led.) to form the fasciculus 

 lateralis, or lemniscus, though the latter are not numerous. Uncrossed secondary tactile tracts {sec. t. 

 rr. rert.) of the fasciculus proprius type enter the formatio reticularis from both the spinal V nucleus and 

 the funicular nucleus. The nucleus ambiguus {nuc. amh.) appears at this level and the canalis cen- 

 tralis begins to dilate into the fourth ventricle. 



Fig. II. Section through the visceral commissural nucleus and nucleus funiculi. The first accessory 

 lobe and spina V nucleus lie farther caudad and the fasciculus dorso-lateralis is terminating in the 

 nucleus funiculi. The most cephalic part of the somatic commissura infima {com inf.) is shown passing 

 between the funicular nuclei. Ventrally of it is the visceral commissural nucleus which contains no 

 medullated commissural fibers, though diffuse unmedullated tracts cross the median line. At this level 

 this nucleus receives the most caudal sensory vagus root {rx. sens, vagi.) The motor vagus root arises 

 from the nucleus ambiguus farther ventrally. Medullated secondary tactile tracts arising in the nucleus 

 funiculi cross in the ventral commissure {sec. t. tr. cruc.) to reach the ventral cornu and ventral funiculi. 

 From this level forward the tractus cerebello-spinalis {tr. cereb. sp.) can be distinguished from the spinal 

 V and adiacent tracts. 



