RAMUS OPHTHALMICUS SUPERFICIALIS. 423 



nating in branches to the skin in front of the eye (PI. 17, figs. 3, 

 VII. ; 4,7, VII. a). It courses close beneath the skin (though this does 

 not appear in the sections represented on account of their ob- 

 liqueness), and runs parallel and dorsal to the ophthalmic branch 

 of the fifth nerve, and may easily be seen in this position in 

 longitudinal sections belonging to stage O ; but its changes 

 after this stage have hitherto baffled me, and its final fate is 

 therefore, to a certain extent, a matter of speculation. 



The two other branches of the seventh, viz., the hyoid or 

 main branch and mandibular branch, retain their primitive 

 arrangement till the close of stage O. 



The fate of the remarkable anterior branch of the seventh 

 nerve is one of the most interesting points which has started 

 up in the course of my investigations on the development of 

 the cranial nerves, and it is a matter of very great regret to me 

 that I have not been able to clear up for certain its later 

 history. 



Its primitive distribution leads to the supposition that it 

 becomes the nerve known in the adult as the ramns optJial- 

 micus superficialis of tlic fifth nerve, and this is the view which I 

 admit myself to be inclined to adopt. There are several points 

 in the anatomy of this nerve in the adult which tell in favour of 

 accepting this view with reference to it. In the first place, the 

 ramus ophthalmicus superficialis rises from the brain (vide 

 description above, p. 417), quite independently of the ramus 

 ophthalmicus profundus, and not in very close connection with 

 the other branches of the fifth, and also considerably behind 

 these, quite as far back indeed as the ventral root of the 

 seventh. There is therefore nothing in the position of its root 

 opposed to its being regarded as a branch of the seventh nerve. 

 Secondly, its distribution, which might at first sight be regarded 

 as peculiar, presents no very strange features if it is looked on 

 as a ramus dorsalis of the seventh, whose apparent anterior 

 instead of dorsal course is due to the cranial flexure. If, how- 

 ever, the distribution of the rarnus ophthalmicus superficialis is 

 used as an argument against my view, a satisfactory reply is 

 to be found in the fact that a branch of the seventh nerve cer- 

 tainly has the distribution in question in the embryo, and that 

 there is no reason why it should not retain it in the adult. 



