667 



Tlie appearance of' the nucleus XI, like that of the ambiguus, is 

 very different; in continuous series of the 1st. cervical segment and 



- -t 



^ 



Fig. 21. Calfs foetus about 41/2 months. 



of the region of it lying here cranially, i.e. at the place wiiere the 

 nucleus by reason of its position between anterior and posterior horns 

 is most sharply defined and therefore easiest to follow, this can 

 be seen very clearly and frequently in the neighbourhood of places 

 where the nucleus is very strongly developed, it will be found that 

 it is greatly reduced, often indeed quite absent. Deks has shown the 

 so-called rosary-shaped development of the nucleus accessorii in 

 longitudinal sections. 



Also as regards the nature of the XI nucleus, various 

 opinions exist. Edinger describes the motor bulbar nuclei as 

 eontin nations of the frontal horn grey matter, which have been 

 disturbed in their continuity, and explains the dorso-medial 

 position, with respect to tlie ventral system of most of 

 them as follows : owing to the upward rise of the central canal, 

 the motory regions lying below rise too, whereby the sensory regions 

 at the same time are pressed laterally. This conception cannot be 

 disputed as regards the tongue nucleus. As for the glosso-pharyngeo- 

 vago-accessorius system, however, the conclusion drawn by Kappeks is 



