306 ALBERT KUNTZ 



origin in the hind-brain and in the vagus gangha and migrate 

 peripherally along the paths of the vagi. These findings agree 

 essentially, in regard to the sources of the cells giving rise to the 

 sympathetic nervous system, with the writer's observations on the 

 histogenesis of the sympathetic nervous system in mammals, 

 birds, and fishes. They disagree widely with all the observations 

 hitherto recorded on the development of the sympathetic nervous 

 system in reptiles. They disagree also with the observations of the 

 earlier investigators on the development of the sympathetic ner- 

 vous system in the other classes of vertebrates primarily in two 

 particulars: (1) some of the cells which enter the anlagen of the 

 sympathetic trunks are found to have their origin in the ventral 

 part of the neural tube and to wander out along the paths of the 

 motor nerve-roots; (this fact was observed by Froriep ('07) in 

 embryos of Torpedo and of the rabbit) ; (2) the vagal sympathetic 

 plexuses are found to bear no direct genetic relationship to the 

 sympathetic trunks, as the earlier investigators supposed, but 

 arise from cells which have their origin in the hind-brain and in the 

 vagus ganglia and migrate peripherally along the paths of the 

 vagi. 



The phenomena presented in embryos of the turtle may throw 

 some new light on the problems involved in the peripheral migra- 

 tion of embryonic nervous elements. 



Among the more recent investigators, Froriep ('07) has sug- 

 gested that the nerve-fibers constitute the vehicles by means of 

 which nervous elements are carried peripherally. According to 

 his view the peripheral displacement of these cells is accomplished 

 either by the growth of the axones alone or by the growth of the 

 axones coupled with the active migration of the cells along the 

 fibers. Held ('09) advanced the theory that the 'so called' 

 wandering of the sympathetic anlagen is brought about by the 

 pressure which is exerted by the mitotic division of proliferating 

 elements in an elongating cell-column, coupled with the formation 

 of peripheral protoplasmic processes which are endowed with the 

 property of contractility and must, therefore, exert a pull in a 

 longitudinal direction as soon as osmotic influences act upon their 

 growing substance. 



