659 



animal, it must not be considered impossible that the XI nucleus 

 extends still further and that XI fibres with cervical nerves leave more 

 distallj, as is the case in the Camelidae, wliere a nervous accessorius 

 spinalis is entirely absent. 



Nucleus liypoghssi. Before the ap|)earance of the XII nucleus the 

 dorsal motor vagus nucleus is well developed and efferent XII fibres are 

 visible; the direct continuation of nucleus XII out of the frontal horn 

 grey matter can be clearly demonstrated in the giraffe as in the 

 lama and the camel (tig. 2), typical large front-horn cells shift to a 

 higher level and soon arrange themselves in a group of XII cells. 

 In this series this occurs 496 sections spinally from the calamus. 

 First a cell-group appears lying ventro-laterally from the canal and 

 consisting of 6 — 10 cells; this group retains the same degree of 

 development in many of the following sections. We see repeatedly 

 fiells in this area between the dorsal motor vagus nucleus and the 

 tongue nucleus; they clearly belong to the vagus nucleus, in the 

 first place by reason of their ty[)e, but in the second place because 

 here there is always some distance between these ventral vagus cells and 

 the tongue nucleus (fig. 15). After this the nucleus XII grows out, 

 first dorso-laterally and then medially in the direction of the raphe. 

 The nucleus then contains 30 — 35 large cells, the majoi-ity attain 

 the maximum diameter of 85 ft; only in the dorsolateral group are 



f- 



'^^X 









(' ' 1 



'^^ 





Kie. 15. Fie. IG. 



