- MITSTELUS- L^-VIS. 209 



presented by Carcliarias certainly needs further investigation, 

 its explanation may perhaps be found in the frequent assertion 

 that the trochlearis is a branch of the ophthalmicus trigemini. 



That in the ascent or descent of one or the other of the 

 ophthalmic nerves one of them could cut through the troch- 

 learis and oculomotorius, temporarily severing their fibres, or 

 that it could cut through the intervening eye muscles distal 

 to the point of attachment of the associated nerve, is not I 

 think assumed by anyone. 



If then a simple juxtaposition of the two nerves, already 

 developed in their typical positions, be eliminated from the 

 discussion, it is evident that any assumed fusion of them pre- 

 supposes, either that one or the other of the two nerves is not 

 primarily developed in its typical position, or that the two 

 nerves develop before the structures that typically separate 

 them have been sufficiently developed to interfere with their 

 juxtaposition and subsequent fusion. The whole question of 

 the development of nerves is thus here involved, and it is not 

 my intention to in any way discuss it. Certain statements 

 regarding the development of the nerves here especially 

 under consideration, and bearing directly upon their relations 

 to other structures in the orbit, deserve however to be given. 



Dixon (15) believes, with His, that the permanent filn'ous 

 nerve grows outward, either directly from the brain, or from 

 the related ganglion. Of the ophthalmic nerve in man, he 

 says (p. 33) that the first-formed fibres of the nerve are 

 deflected from their primary direction by reason of some cor- 

 relation to other growing tissues, and that they become the 

 nasal branch of the ophthalmic nerve of the adult. Later 

 fibres, not similarly obstructed, continue in the primary direc- 

 tion of the ophthalmic nerve and form the frontal branch of 

 the nerve of the adult. We thus have, under this theory of 

 the development of nerves, a statement which certainly in- 

 volves, in principle, the change of a nerve from the position of 

 a superficialis to that of a profundus. Because of its position 

 Dixon considers tlie frontal nerve as the probable homologue 

 of the portio trigemini of the ophthalmicus superficialis of 



