558 Dr. G. E. Nicholls. Intracranial Ganglion upon the 



This is not only definite confirmation of Sherrington's suggestion that the 

 third nerve is sensori-motor, but it also points to a connection between these 

 ganglionic cells and afferent fibres from sensory end-organs (the muscle- 

 spindles). It thus affords evidence that these cells are of a type normally 

 occurring elsewhere only upon the dorsal roots of segmental nerves. 



In summing up, Miss Tozer remarks* " The great variation in the number 

 of these cells renders an explanation of their nature and function at present 

 impossible. The cells in Gaclus are possibly sufficiently numerous to represent 

 the source of the afferent fibres .... but in Macacus the number of these 

 cells seems to be insufficient to do this." If the latter part of the statement 

 is correct, some of the afferent fibres presumably have an intracerebral origin. 



Since the oculomotor nuclei are in close relation to several sensory centres 

 through the mediation of the fasciculus longitudinalis, there is nothing 

 improbable in the suggestion that some of the afferent fibres may pass directly, 

 by the fasciculus longitudinalis, to one of these centres. 



The Relation, in Development, of the Ciliary Ganglion to the Oculomotor. — 

 Carpenter ('06, p. 192) has demonstrated that while, in the embryo chick, 

 the ciliary ganglion arises, in part, from cells which have migrated from the 

 ophthalmicus profundus ganglion, it is also, to some extent, derived from 

 neuroblasts which pass peripherally along the fibres of the oculomotor nerve 

 to the ciliary ganglion. 



In view of this statement I was, at first, inclined to believe that the oculo- 

 motor ganglia which I had observed were merely cell masses destined primarily 

 for the sympathetic system but which had been arrested at this place in their 

 transit to the ciliary ganglion. Such an explanation, however, merely introduces 

 another difficulty, viz., the apparently anomalous origin of the ciliary ganglion. 



In a typical segmental nerve, sympathetic ganglia are generally believed to 

 arise by the migration of neuroblasts from the spinal ganglion upon the dorsal 

 root.f The alternative view that sympathetic ganglia arise, either wholly or 

 in part, by the migration of medullary cells along a ventral nerve root has 

 met with little acceptance. The former view is that favoured by Neal. In 

 an earlier work, that author maintained ('03) that, although the cells in the 

 anlagen of the spinal ventral roots had a medullary origin, yet these had 

 nothing to do with the formation of neuraxons. They are differentiated solely 

 into neurilemma elements. In his recent work he notes ('14, p. 54) that this 

 fact has never been called in question but that, on the contrary, it has been 

 confirmed by several subsequent workers. 



Concerning Carpenter's statement that neuroblasts pass along the oculo- 



* Op. cit., p. xvi. 



t Of Johnston, '07, p. 206. 



