George L. Streeter 



101 



adult specimen. This shows the presence of persistent clumps of normal 

 appearing ganglion cells, situated along the trunk of the eleventh and on 

 the roots of the ninth and tenth nerves. A diagrammatic reconstruction 

 of the series is shown in Fig. 13. In this case the first cervical nerve 

 received a communicating branch from the accessory, but macroscopically 

 no ganglion was present. In the series, however, this ganglion is repre- 

 sented by a circumscribed group of cells on the trunk of the accessory. 

 Among the rootlets in the same region are scattered groups of cells Avhich 

 may have been separated off from it. On going further forward other 

 small ganglion groups are met with, either just beneath the connective 

 tissue sheath of the nerve roots, or among their fibres, and usuallv near 



ace essory root ganglia 



rtymp 



Gang 

 petros 



Gang nodosum. 



Fig. 13. Diagrammatic reconstruction of ganglion cell masses in peripheral nerves of 

 occipital region in human adult. Compare with Plate IV. 



the junction of the roots with the larger trunks. From their posi- 

 tion these are considered to be the persistent accessory root ganglia. 

 Although rudimentary in size they are made up of cells which have all 

 the appearances of functionating ganglion cells. It is possible that it is 

 these that provide the sensory fibres for that branch of the accessory 

 which joins with fibres from the vagus to form the pharyngeal branch, 

 in some such way as is schematized in Plate IV. 



Development of Individual Xerves. 



It has been seen, in tracing the development of the ganglionic crest of 

 the after-brain, that the ninth nerve stands apart from the more caudal 

 nerves and develops independently, and apparently uninfiuenced by them. 

 The tenth and eleventh, in contrast, are parts of a single complex, and 

 cannot be taken up as individual structures without adopting a sepa- 



