54 H. V. NEAL 



is exclusively medullary. In the trout some of the cells possibly 

 come from the dorsal ganglia, while in the Amphibia they come 

 exclusively from this source. In reptiles, birds and mammals 

 they appear to come chiefly from the sensory ganglia. 



According to the writer ('03) the cells of somatic motor nerves 

 of Squalus have a medullary origin. Figures 12 to 32 (pis. 23-24) 

 show the gradual transformation of cells into the neurilemma 

 of the adult. Since the fact is unquestioned there appears no 

 reason for repeating the evidence upon which this conclusion 

 is based. Bardeen ('03), Carpenter ('06), Carpenter and Main 

 ('07), also drive the neurilemma from migrant medullary cells. 

 Kuntz ('10) confirms this conclusion. 



But is it not possible that the medullary elements contained 

 in somatic motor nerve anlagen enter into the formation of the 

 sympathetic? Such a fate has been claimed for them by more 

 than one competent investigator. 



10. To ivhat an extent do the emigrated medullary elements enter 

 into the formation of the sympathetic ganglia? 



In recent j^ears the Remak-Kolliker view that the sympa- 

 thetic system is of mesodermal origin has been shared by few 

 investigators. Onodi ('86) considered such an origin as possible 

 for the peripheral sympathetic plexuses and both Paterson ('90) 

 and Fusari ('90) have held the same view of the genesis of the 

 elements of the sympathetic. 



Balfour ('78) and Schenk and Birdsall ('78) led the way to the 

 present understanding of the ectodermal origin of the sympa- 

 thetic. Balfour did not decide whether the sympathetic cells 

 were derived from dorsal or ventral roots, but Schenck and 

 •Birdsall inferred their origin from the dorsal ganglia, a conclu- 

 sion since drawn by Onodi ('86), VanWijhe ('89), His ('90), 

 His, Jr. ('91, '97), von Kollicker ('94), C. Rabl ('97), Kohn 

 ('05, '07), Lillie ('08), Held ('09) and Marcus ('09). 



Hoffmann ('00) inferred a double source of origin of the sympa- 

 thetic elements as derivatives both of the dorsal and ventral 

 roots, an opinion shared by Neumayer ('06) and Kuntz ('11). 



