George L. Streeter 113 



Often the connection between the ventral root ot the first cervical and its 

 ganglion is also missing in man, and the ganglion rudimentary and found 

 only on section. These rudimentary ganglia during embryonic life 

 become adherent to the invading cranial member, the accessory nerve, and 

 though all connection with the ventral root is absent, they still may func- 

 tionate by sending their fibres forward or backward along the accessorius, 

 in the latter case joining a more caudal nerve. Although the first cervi- 

 cal ganglion, and perhaps a precervical or Froriep's ganglion may thus 

 lie in the tract of the accessorius, it is to be remembered that embryologi- 

 cally they are separate structures, the one cranial and the other spinal. 

 The apparent relation between the two is only due to the fact that in 

 the early stages they lie closely together, and become adherent in this 

 position. 



In addition to these occipito-spinal (precervical, hypoglossal, or 

 Froriep's) ganglia, there are found in the human adult other rudiment- 

 arj^ ganglia situated along the accessory nerve, which are of cranial origin, 

 and similar to the root ganglion of the vagus. These are the accessory 

 root ganglia; they form, in the six weeks embryo, a series of ganglionic 

 clumps, which extend caudalward from the ganglion jugulare, successively 

 diminishing- in size, along the tract of the accessory nerve attached to its 

 rootlets. A true segmental arrangement of them does not seem to prevail 

 in the human embryo, and the same is true in dissections of pig embryos. 

 The ganglion jugulare continues to develop, but these accessory ganglia 

 early reach a size beyond which they do not further develop. They, 

 however, do not imdergo retrograde metamorphosis, at any rate not 

 completely, for evidence of them may still be found in the human adult. 



The root ganglia of the ninth, tenth, and eleventh nerves develop from 

 a ganglion crest which has an appearance and history analogous to that 

 from which the spinal ganglia develop. The ganglia whicli form on the 

 trunks of the vagus and glosso-pharyngeus apparently develop independ- 

 ently from that crest, and they differ from the ganglia of the roots in 

 being branchio-meric, and in possessing definite traces of rudimentary 

 sense organs. 



The hypoglossus in contrast to the tenth and eleventh nerves, which 

 show no trace either in rootlets or ganglia that they w^ere ever formed 

 from a series of segmental nerves, presents a distinct segmental grouping 

 of its fibres, as may be seen in Plate I and Fig. 1. This fact, added to 

 its resemblance in its early stages to tbe ventral roots of the cervical 

 nerves in point of origin from the same column of cells, its relation to the 

 myotomes, and the occasional presence of a Froriep ganglion, offer con- 

 clusive evidence that this nerve is the equivalent of three or four ventral 



