336 ALBERT KUNTZ AND O. V. BATSON 



advance peripherally along the paths of the dorsal and ventral 

 roots of the spinal nerves respectively. They are identical in 

 appearance; consequently, in embryos of the higher vertebrates, 

 those from the one source cannot be distinguished from those 

 from the other source after they have advanced beyond the junc- 

 tion of the dorsal and ventral nerve-roots. Therefore, the fact 

 that cells deviate from the paths of the spinal nerves and enter 

 the prunordia of the sympathetic trunks does not prove conclu- 

 sively that these primordia comprise both cells of ganglionic and 

 medullary origin. The chief contentions of those who maintain 

 that only cells which advance peripherally from the spinal ganglia 

 enter the primordia of the sympathetic trunks are: 1) that mi- 

 gration of cells from the ventral part of the neural tube, if it 

 occur at all in embryos of the higher vertebrates, is not abun- 

 dant, and 2) that such cells as may advance from the neural tube 

 along the fibers of the ventral roots of the spinal nerves become 

 incorporated in the neurilemma. 



In view of the present status of this problem it has seemed de- 

 sirable to obtain crucial experimental evidence regarding the 

 contribution of cells from the neural tube to the prunordia of the 

 sympathetic trunks. If the neural crests and the dorsal portion 

 of the neural tube could be eliminated before the spinal ganglia 

 have become differentiated and the embryo could continue to 

 develop without spinal ganglia and dorsal nerve-roots, the re- 

 maining portion of the neural tube would be the only source from 

 which cells of nervous origin could migrate along the paths of 

 the spinal nerves. If in such embryos the primordia of the sym- 

 pathetic trunks should arise, they would of necessity arise from 

 cells which migrate from the neural tube along the paths of the 

 ventral roots of the spinal nerves. 



The obser^'ations set forth in this paper are based on embryos 

 of the chick which were early subjected to an operative proced- 

 ure by which the dorsal portion of the cerebrospinal nervous 

 system was destroyed throughout a limited portion of the trunk 

 region. This material affords conclusive evidence that cells of 

 medullary origin which advance peripherally along the ventral 

 roots of the spinal nerves enter the primordia of the sympathetic 

 trunks. 



