MEDULLA OBLONGATA 171 



which I provisionally identified in Necturus ('14, p. 8) and subse- 

 quently ('17, p. 250) questioned and the presence of which has been 

 confirmed by Larsell. 



In the light of such fragmentary evidence as we now have, it seems 

 to me probable that in Amblystoma the ascending tertiary visceral- 

 gustatory fibers take a deep course, accompanying the brachium con- 

 junctivum, and that the superficial fascicle described above is a 

 mamillo-cerebellar tract, which also connects with the isthmic teg- 

 mentum and the isthmic visceral-gustatory nucleus. 



The bulbar apparatus of visceral-gustatory adjustment is simply 

 organized in Amblystoma, as, indeed, it is in man, with minimal pro- 

 vision for local specialization. The division of the ascending path into 

 dorsal and ventral moieties in the isthmus is similar to the diver- 

 gence of the olfactory paths to epithalamus and hypothalamus. In 

 both cases somatic correlations are effected dorsally and olfacto- 

 visceral correlations ventrally. The dorsal gustatory nucleus may 

 directly activate the skeletal musculature concerned with feeding, 

 through its connections with the underlying tegmentum, or it may 

 discharge into the hypothalamus, where all visceral adjustments are 

 organized. 



The swallowing of a morsel of food in response to excitation of taste 

 buds is one of the simplest acts of which the body is capable. This may 

 be done reflexly through the local activation of the bulbar connec- 

 tions of the f. solitarius; but, simultaneously with this local action, 

 nervous impulses may be transmitted to higher centers which are so 

 interconnected as to bring this simple act into relation with any 

 other activities that may be in process in response to internal or ex- 

 ternal stimuli. The final result of any particular sensory excitation 

 is dependent upon the central excitatory state of the central nervous 

 system as a whole and of every local part of it. And the quality of 

 this excitatory state is determined not only by the stimuli presently 

 acting upon it but also by the^past experience of the race and of the 

 individual. This theme is amplified in a recent discussion of the ap- 

 paratus of optic and visceral correlation ('44a). 



