SYMPATHETIC SYSTEM IN MAMMALS 



243 



totic figures occur frequently in the ganglion of the trunk and 

 occasionally all along the vagus nerve. 



The course and the direction of the cells migrating peripherally 

 along the fibers of the vagi are indicated by the arrows in fig. 16. 

 That these cells actually migrate peripherally cannot be doubted. 

 The number of "accompanying" cells present in the vagus trunks 

 increases rapidly until a maximum number is reached in embryos 

 9 or 10 mm. in length; then it decreases rapidly until the embryos 



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nb. 



6 *% 







vfli/r-, ; f 



Fig. 15. Section through the rootlets of the vagus nerve in an embryo 10 

 mm. in length, taken at right angles to the axis of the trunk, X 270. 



have attained a length of about 13 mm., when only a relatively 

 small number of cells remains distributed along the nerve-fibers. 

 These phenomena can be explained on no other ground. Again, 

 the preparations studied show figures of cells escaping from the 

 growing branches of the vagi into the anlagenof the cardiac plexus 

 and the sympathetic plexuses in the walls of the visceral organs 

 which are perfectly clear, and can be interpreted only to mean 

 that these are the cells which give rise to the vagal sympathetic 

 plexuses. 



The majority of the cells migrating peripherally along the fibers 

 of the vagi are characterized by large rounded or elongated nuclei 

 showing a delicate chromatin structure, and very little cytoplasm. 



