252 ALBERT KUNTZ 



Therefore, the sympathetic neurones are homologous with the 

 neurones in the central nervous system. 



The sympathetic system is not a nervous mechanism separate 

 from the central nervous system, but the nervous system is a 

 unit of which the sympathetic system is a part homologous with 

 the other functional divisions. It may be looked upon as an acces- 

 sion to the nervous system which has arisen comparatively late 

 in the evolution of vertebrates, in response to an increasing demand 

 for a nervous mechanism of a lower order, which might assume 

 the direct control of the purely vegetative functions. 



(/) Functional relations. — The reader will, undoubtedly ask 

 what bearing the facts set forth in the preceding pages may 

 have on physiological and psychological problems involving the 

 sympathetic system. This question we cannot hope to answer 

 at present. We may, however, offer a few suggestions which 

 have presented themselves during the progress of this investiga- 

 tion. 



Our knowledge concerning the functional relations and the 

 physiological activities of the sympathetic system is very limited. 

 Nor could we hope for much progress in this direction as long as 

 the developmental relationships of the sympathetic to the cen- 

 tral nervous system were not definitely known. The fact that 

 the sympathetic system is homologous with the other functional 

 divisions of the nervous system lends a new aspect to the entire 

 problem. The fact, however, that the vagal sympathetic plex- 

 uses have their origin in the hind-brain and the vagus ganglia will 

 probably be of even greater physiological and psychological im- 

 portance. This fact indicates a close relationship between the 

 lower centers of the brain and the innervation of the heart and 

 the visceral organs. The suggestion is here ventured that in 

 this relationship will probably be found the basis of certain phy- 

 siological and psychological problems involving the digestive 

 functions and the action of the heart, which have hitherto been 

 obscure. 



Here is a field for investigation which challenges the attention of 

 both the student of physiology and the student of psychology. 

 It is beset with the* greatest difficulties, but promises to be fruit- 

 ful of the most far-reaching results. 



