CRANIAL SYMPATHETIC GANGLIA IN THE RAT 165 



the type most prevalent in the sympathetic nervous system, and 

 that consequently the direction of migration of cell bodies of 

 sympathetic neurons forms no exception to the expressed 

 generalization. 



In the application of this principle to the problem of the head 

 sympathetic, Kappers draws certain conclusions: In fish forms 

 the possibility of stimulation of sensory endings of cranial visceral 

 nerves is in excess of the possibility of stimulation of spinal 

 visceral branches, at least so far as concerns nerves VII, IX, and 

 X. Sensory branches are spread over gills and adjacent regions 

 exposed to strong stimuli, while branches to the viscera them- 

 selves, hidden as they are, are much less open to stimulation. 

 In higher vertebrates the visceral territory of the sensory VII, 

 IX, and X components is relatively less open to powerful stimu- 

 lation than is the corresponding territory in lower forms, since 

 gills are absent and feeding methods vary. Furthermore, 

 throughout the alimentary tract, sensory terminations are in- 

 ferior in numbers to motor terminations. Kappers therefore 

 infers that, in the absence of true sensory (reflex) stimulation, 

 the axon type has dominated the system. As an expression of 

 this increasing want of adequate sensory stimulation in the head 

 region of higher forms and the consequent domination of the 

 axon type would come, I should suppose, the development of such 

 structures as the otic, sphenopalatine, and submaxillary ganglia. 

 The factor, according to Kappers, influencing the development 

 of a series of cranial sympathetic ganglia in teleosts, is probably 

 the protecting value of the operculum. In criticism of this 

 largely theoretical work, numerous objections may be raised: 

 first, while it might possibly explain the absence of cranial sympa- 

 thetic ganglia developed in connection with cranial nerves in 

 general, it could scarcely account for the fact that when sympa- 

 thetic ganglia do appear, they are developed in connection with 

 the trigeminus — should such be the conclusion eventually reached ; 

 secondly, quantitative estimations for relative possibilities of 

 stimulation are little more than suppositions, and Kappers must 

 certainly consider, in this connection, the difference between 

 strength of stimulus and adequacy of stimulus; thirdly, there is 



