302 ALBERT KUNTZ 



in embryos of Torpedo and of the rabbit only in regard to the 

 sympathetic trunks and the prevertebral plexuses. Froriep suc- 

 ceeded in tracing medullary cells from the neural tube into the 

 ventral roots of the spinal nerves. According to his observations 

 these cells, with similar cells which wander out from the spinal 

 ganglia, migrate peripherally along the spinal nerves. At the 

 origin of the communicating rami, cells deviate from the courses 

 of the spinal nerves and give rise to the sympathetic nervous 

 system. Inasmuch as Froriep does not admit of the existence of 

 sympathetic sensory neurones, he concludes that all the sympa- 

 thetic neurones in the sympathetic trunks and the prevertebral 

 and the peripheral sympathetic plexuses arise from cells which 

 have their origin in the ventral half of the neural tube and migrate 

 peripherally along the ventral roots of the spinal nerves. My 

 observations have shown conclusively that the cardiac plexus and 

 the sympathetic plexuses in the walls of the visceral organs do 

 not arise from cells which migrate peripherally along the spinal 

 nerves, but have their origin in cells which migrate from the hind- 

 brain and the vagus ganglia along the vagi. As I have pointed 

 out in an earlier paper, experimental evidence indicates the exist- 

 ence of sympathetic sensory neurones in some of these plexuses. 

 It is probable, therefore, that the sympathetic excitatory neurones 

 arise from cells which migrate from the neural tube along the 

 fibers of the motor nerve-roots, while the sympathetic sensory 

 neurones, wherever such neurones exist, arise from cells which 

 migrate peripherally from the cerebro-spinal ganglia. According 

 to this interpretation, the sympathetic neurones are homologous 

 with the afferent and the efferent components of the other func- 

 tional divisions of the peripheral nervous system. 



Froriep further believes that the axones which constitute the 

 fibers of the motor roots of the spinal nerves are the vehicles by 

 means of which medullary cells are transported peripherally along 

 the spinal nerves, and that cells are carried from the spinal nerves 

 into the anlagen of the sympathetic trunks by the axones which 

 constitute the motor fibers of the communicating rami. He is 

 not convinced as to whether such peripheral transportation is 



