658 



the same conditions as before. Locally again one medial and 

 one lateral portion of the nucleus occurs, or either one of the two 

 portions, or cells in the middle horn are seen. The contact with 

 frontal horn cells is then present again. The same process repeats 

 itself several times and the medial part, in the direction therefore of the 

 place where the dorsal motor vagus nucleus will shortly appear, 

 is frequently met with better developed than before. In this series 

 we thus see in the first cervical segment, varying frequently at the 

 place already mentioned, an extremely poor development of the 

 accessorius nucleus, followed by a gradual strengthening and an 

 outgrowth of it, both in a medial and in a lateral direction, together 

 with a contact with front horn ceils (or shifting in a ventro-lateral 

 direction) till the dorsal motor vagus nucleus appears and the 

 repeated merging of the latter with the XI nucleus begins, as has 

 been mentioned in the description of the said vagus nucleus (fig. 2). The 

 last union of the two nuclei occurs 40 sections spinally from the 

 appearance of the first XII cells, in a region where the frontal horns 

 are still well developed and nothing is to be seen of the oliva inferior. 



Also in the VVkigert-PaIj, van Gieson and Sheldon series the XI 

 nucleus was in the first cervical segment to be seen at the place 

 already indicated. The ending of the nervus accessorii could be traced 

 in many sections. Frequently we see several bundles leave through 

 the processus posterolateralis of Ziehen, often three parallel to each 

 other, first an upward arch, parallel to the distal portion of the posterior 

 horn, and then laterally. These bundles do not leave the nucleus 

 directly, but first take a medial curve before leaving grey matter. 

 In a few preparations it was obserxed that fibres joined these bund- 

 les from a more centrally situated region, and also from a more 

 ventrally situated region. Besides the above bundles fibres also leave 

 the XI nucleus and a little further distally, directly i.e. without a 

 central curve. Also in the 2nd. cervical segment efferent XI roots 

 were to be seen, but far fewer in number and of poorer develop- 

 ment than in the 1st. Only in a few sections could indications of 

 the XI nucleus be demonstrated on the border of the anterior and 

 posterior horns, though in several sections cells could be seen in the 

 processus postero-lateralis, through which the efferent root takes its 

 way. Judging from the great decrease in the efferent XI roots in 

 the 2nd. cervical segment, it may be assumed that in the giraffe 

 the nervus accessorius spinalis extends only to the 2nd. cervical 

 segment, or perhaps a little further distally of it. In view, however, 

 of the important function this nerve has undoubtedly to fulfil in this 



