NEAL: NERVOUS SYSTEM IN SQIJALUS ACANTHIAS. 273 



lateral, or ventral indicates that the point of view of morphologists 

 is now fundamentally different from that of the older anatomists, who, 

 in dealing with the question of the segmental value of cranial nerves, 

 excluded the eye-muscle nerves from consideration on the ground of 

 their inconstancy in appearance and distribution. Except on the part 

 of Froriep, Kastschenko, and Rabl, who regard the pre-otic region as 

 one sui generis, I find no tendency to revert to the view of Stannius 

 ('49, p. 125) that " der Parallelisirung der Augenmuskelnerven mit 

 Spinalnerven stellen sich, wegen ihrer eigenthtimlichen Ursprungs- 

 verhaltnisse, des ihnen zukommenden Mangels von Ganglien und der 

 ausschliesslichen Vertheilung ihrer ungemischten Primitivrohren in den, 

 auch ihrerseits mit Muskeln der Wirbelsaule durchaus nicht vergleich- 

 baren, Muskeln eines Sinnes-Apparates so unliberwindliche Schwierig- 

 keiten entgegen, dass von einer solchen nicht fliglich die Rede sein 

 kann." However, the labors of comparative anatomists, among whom 

 may be named Huxley, Gegenbaur, M. Fiirbringer, and Schwalbe, during 

 the thirty years following the work of Stannius just quoted, resulted 

 in so well establishing the " Blirgerrecht " of the eye-muscle nerves 

 that morphologists now assume that they are comparable with either 

 dorsal or else ventral segmental nerves. Only a minority of anatom- 

 ists, among whom may be named Schneider ('79), van Wijhe ('82), 

 Beard ('85), His ('88»), Dohrn ('91), Neal ('96), and M. Fiirbringer ('97), 

 have regarded them as ventral segmental nerves. The weightiest well 

 established evidence in favor of this view was first stated by His ('88), 

 and consists in the fact that the eye-muscle nerves, at least of the adult, 

 resemble ventral spinal nerves both in histological structure and in the 

 situation of their motor nucleus in the ventral horn of the neural tube ; 

 and also in the less well established fact that they innervate muscula- 

 ture derived from segments of the dorsal mesoderm. On the other 

 hand, the majority of morphologists, among whom may be named Bal- 

 four (78), Marshall ('81), Dohrn ('85, '87, '90), Gaskell ('89), Hoff- 

 mann ('89, '94), Oppel ('90), Houssay ('90), Piatt ('91), Froriep ('91), 

 Zimmerraann ('91), Hatschek ('92), Mitrophanow ('92, '93), and Kupffer 

 ('94, '95, '96), while in general of the opinion that the abducens is the 

 homologue of one or more segmental ventral nerves, have held that 

 either the trochleai'is or the oculomotorius, or both, represent dorsal (or 

 lateral) segmental nerves. The chief arguments in favor of this view 

 consist in evidence (1) of the development of these nerves from neural- 

 crest cells ; (2) of a cellular or so called ganglionic structure of the 

 nerves in the embryo ; (3) of transitory or permanent ganglia in con- 



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