Bremer, Aberrant Roots. 637 



as noted above, the hypoglossal nerve roots have true dorsal rami, 

 running to the muscles corresponding to the trapezius, and where 

 the accessory nerve is very small (containing only the visceral 

 efferent fibers). The probability that this is a correct theory is 

 further strengthened by the finding of the laterally running 

 aberrant roots, described above, which could be easily explained 

 as fibers from cells in the nucleus ambiguus, belonging with the 

 ventro-lateral component, which run with the ventral root and 

 then turn dorsally, as in the cord, instead of with the lateral root. 

 (Fig. 9, diag. C). 



TABLE. 



(The sensory components have not been Hsted) 

 Nerve. Motor components. 



Ill ventro-mesial. 



IV ventro-mesial and visceral efferent ( ?). 



V \dsceral efferent. 



VI ventro-mesial (probably belongs with V). 



VII visceral efferent. 



IX visceral efferent, (aberrant embryonic ventro-mesial and ventro- 

 lateral components.) 



X] r ventro-mesial (XII and aberrant). 



XI 1- I ventro-lateral (X and XI, and aberrant). 



XII J [visceral efferent (X and XI). 



It is not necessary to trace the components of the other cranial 

 nerves separately; the accompanying table gives them in outline. 

 The ventro-mesial efferent component is present, with a slight 

 gap (and that this gap is potentially absent is shown by Bdellos- 

 toma, and by the ventral roots I have found in embryos) as far for- 

 ward as the oculomotor nerve. The ventro-lateral efferent com- 

 ponent is present as far forward as the nucleus ambiguus extends. 

 Here a word of explanation is necessary. Fibers from the nucleus 

 ambiguus run in the glossopharyngeal and facial nerves, and I 

 expect that it will be found that many of the outer muscles inner- 

 vated by these nerves are really not derived from lateral mesoderm, 

 like the pharyngeal muscles, but are myotomic muscles, comparable 

 with limb muscles. This would account for the anastomoses 

 between the infra-mandibular branch of the facial nerve, for 

 instance, and branches of the cervical nerves; and for the presence 

 of the laterally running aberrant roots which pass in front of the 

 vagus. 



The visceral efferent component is present in the lateral motor 

 roots of the cranial nerves as far forward as the trigeminal, and 



