MEDULLA OBLONGATA OF AMBLYSTOMA 355 



fibers, tract h of Kingsbury. Above this are found in sequence 

 the ventral lateraHs X root, the ventral lateralis VII root, the 

 dorsal lateralis X root, the middle lateralis VII root, the longitu- 

 tudinal correlation tract a of Kingsbury, and the dorsal lateralis 

 VII root. 



The detailed relations of the somatic sensory roots of the 

 cranial nerves will next be described. This will be followed by a 

 description of the visceral sensory roots of these nerves and of the 

 correlation neurones and fiber tracts with which all of these various 

 roots stand in physiological relation. 



The lateral line roots of the facialis. These form the dorsal VII 

 (Vllb) of Strong ('95) and Kingsbury ('95) and VII u and 1 of 

 Osborn ('88). Coghill ('02, p. 217) describes the lateralis VII root 

 of old larvae and adults of Amblystoma tigrinum as entering the 

 brain in four subdivisions, of which the first and third, counting 

 from the dorsal side, lie father caudad than the other two. The 

 fibers of the first and third of these subdivisions come from the 

 ramus mentalis VII » via the truncus hyomandibularis ; those of 

 the second subdivision come from the ramus ophthalmicus super- 

 ficialis VII; and those of the fourth come from the ramus buccalis 

 VII. 



In the 38 mm. larva the entire lateralis VII root complex 

 enters the brain in one transverse plane (fig. 11) and I am not able 

 to identify all of Coghill's four subdivisions with certaintj^ I 

 recognize three roots, defined with reference to their relations 

 with other fiber tracts of the oblongata. These are, counting 

 from the dorsal side, (1) the dorsal root {r.VII.l.l.d.), entering 

 dorsally of Kingsbury's tract a; (2) the middle root (r.VII.l.l.m) 

 entering between tract a and the dorsal lateralis X root; (3) the 

 ventral root (r.VII.l.l.v.), entering ventrally of the dorsal lateralis 

 X root and dorsally of the ventral lateralis X root and tract 6 of 

 Kingsbury. The entire complex lies above and enters some- 

 what rostrally of the VIII roots. 



The dorsal lateralis VII root is composed of finer fibers than 

 either of the other two. These bifurcate immediately upon en- 

 trance into the oblongata and both the ascending and the descend- 

 ing branches terminate in an area of neuropil which forms the 



