387 



doubted. In many sections medullary cells are observed drawn out 

 into cone-shaped heaps in the nerve-rootlets as they traverse the 

 marginal veil, and occasionally one of these cells is observed half 

 in and half out of the neural tube. Outside the external limiting 

 membrane the nerve-rootlets contain numerous cells. 



In sagittal sections the entire vagus nerve is observed to contain 

 many of these "accompanying" cells which are apparently migrating 

 peripherally. The ganglion of the trunk is at this stage a large some- 

 what irregular oval or elliptical body which is not sharply limited 

 distally. Groups of cells appear to become separated from its distal 

 end and to wander peripherally along the nerve fibers. Mitotic figures 

 occur frequently in the ganglion of the trunk and occasionally all along 

 the vagus nerve. 



The great majority of the cells migrating along the course of the 

 vagus nerves are characterized by large rounded or elongated nuclei 

 which show a delicate chromatin structure and are accompanied by 

 very little cytoplasm. These are obviously the "indifferent cells" of 

 ScHAPER. Among these, other 



cells occasionally are found ^<9\ (^\ \ /^ 

 which are characterized by large vi;i^ ^|u tw^ 

 nuclei, usually rounded or taper ^ /> 



ing toward one end, which show ..^^^ ,?. 



a distinct nucleolus and very M^ ^P 



little chromatin structure and q) g 



are accompanied by a larger 



- -11 1 • 1 • 1 Fig. 4. Neuroblasts located outside of 



cytoplasmic body which is drawn medullary tube. X 600, drawn with the aid 



out to a point at one side of the camera lucida. a in ventral root of 



.^. J T /\ rrii 11 spinal nerve; h in spinal nerve-trunks; c in 



(rig. 4 a^ e, \.). inese cells communicating ramus; d in rootlet of vagus 



answer to the description of nerve; e and / in vagus trunk. 



the "neuroblasts" of Schaper. 



They may have wandered out as such or have become transformed 



in the course of their migration. 



Conclusion. 



Although, among recent writers who have investigated the develop- 

 ment of the sympathetic nervous system, Kohn ('07) has rejected the 

 theory of the migration of nervous elements. There can be no doubt, 

 in the light of recent researches, that such elements migrate peri- 

 pherally in considerable numbers, both from the neural tube and the 

 cerebrospinal ganglia ^). 



1) A critical review of the literature will appear in a later paper. 



25* 



