742 A. SUBBA KAU AND p. U. JOHNSON ON THE NEllVOUS 



As excellent historical reviews of this suhject can be found in 

 the papers of Kuntz (11), Goormaghtigh (6), and Da Costa (3), 

 and in the 'Text- Book of Human Embryology" of Keibel and 

 , Mall, we do not attempt a further summary, but confine our- 

 selves to a restatement of previous observations on the primary 

 and secondary sympathetic chains in birds and in svich other 

 , vertebrates as have been observed to possess them. 



Wm. His, Jun. (8), was the first to describe the occurrence in 

 chick embryos of primary and secondary sympathetic chains. 

 He observed, in a 4-da.y chick, a sympathetic cliain similar to 

 that found in other vertebrates, i. e. situated immediately behind 

 (i.e. dorsal to) the carotids and on each side of the doi'sal aorta. 

 At the 8th day, however, he found a second cord immediately 

 in front of the anterior (ventral) roots of the spinal nerves. 

 This second cord, he says, soon : outgrows the former in size and 

 is enclosed in the vertebrarterial canal. He was unable to trace 

 the subsequent fate of the primary cord. 



In a later paper (9) the same author again discusses the rela- 

 tions between the primary and secondary cords. He is of opinion 

 that the primary cord in the neck region atrophies, whilst in the 

 thoracic and abdominal regions it forms the aortic plexus and 

 thence migrates along the mesentery to the organs situated in 

 those regions'. He regards the primary sympathetic of the trunk 

 region as only a step on the path of the sympathetic cells from 

 the spinal ganglia to the peripliery, and lays considerable stress 

 upon the resistance oflered to the migratory nerve cells by the 

 mesodermal elements. 



The secondary sympathetic cords he describes as the latest 

 formation of the spinal ganglia, and suggests that the formation 

 of the former ;is due either to a loss of migratory power in the 

 sympathetic cells or to an increased resistance ofi'ered by the 

 niesoblnst. 



Miss W. Abel (1) adopts the views put forward by His, Jun,, 

 but has observed a small contribution from the primary to the 

 secondai-y sympathetic cord, altliough she lays little stress on 

 her important obsei'vation. 



Ivuntz (11) and Ganfini (5) support the main findings of His. 

 They have also observed in Chelonia the existence of a secondary 

 sympathetic. All these writei-s are agi-eed in describing the 

 secondary sympathetic as a new foi-mation quite independent 

 from the primary sympathetic S3'steni. 



A. llelaiions of the Sympatheiic Primordiwjii to the JVeural Crest. 



While Held (7) derives the sympathetic primordia exclusively 

 from the dorsal root ganglia, and Kuntz (12) is of opinion tliat 

 the chief part is derived by way of the ventral roots, our obser- 

 vations lead us to support the view put forward by Streeter (12), 

 He writes : " As the neural ciest becouies detached and its 

 segmenting part invades the space between the myotomes and 



