88 RICHARD ASSHETON. 



inner wall of the optic cup, and, piercing the outer wall, make 

 connection with the outer face thereof. 



2. The optic nerve is formed by the growth of nerve-fibres 

 either from the retina (outer wall of the optic cup) or from 

 the brain, along the optic stalk, but outside it and uncon- 

 nected with it. 



The first of these views has been held by Balfour (1), Had- 

 don (8), Foster (6), Marshall (19), &c. ; while the second 

 view has been held by His (10, 12), Miiller (20), Kolliker 

 (14), Hertwig (9), Orr (21), and more recently supported by 

 Keibel (13), Froriep (7), and Cajal (3). 



In the new edition of ' Quain's Anatomy ' Professor Schafer 

 seems to be uncertain which view to take. He writes on 

 p. 79, " The optic nerves take origin as hollow outgrowths of 

 the brain, which afterwards become solid, while nerve-fibres 

 become developed in their walls. Their mode of origin will 

 be further treated of in connection with the development of 

 the eye." On p. 85 Professor Schafer gives what appears 

 to be an abstract from O. Hert wig's ' Lehrbuch ' (9), pp. 

 402 — 406, in which Hertwig gives His's more recent opinions 

 on the subject. 



His (10) originally considered it probable that the nerve- 

 fibres arose within the brain and travelled towards the retina, 

 but recently (12) has changed his views, and considers it more 

 likely that they arise from neuroblasts within the retina and 

 grow centralwards. 



Thus it seems that the tendency of writers of this country 

 is to adhere to the older view in spite of strong evidence in 

 favour of the newer advanced by foreign authors. 



Moreover, if we accept the theory that all nerve-fibres are 

 outgrowths from nerve-cells, we have the advantage of know- 

 ledge of a peculiarly fascinating nature, and the comprehen- 

 sion of the structure and development of the central nervous 

 system is rendered clearer to both teacher and pupil. 



The beautiful works of His, Cajal, and others — but more 

 especially of His — having once taught us what to look for, 

 it is an easy matter with ordinary care in the preparation of 



