272 ELEMENTARY PHYSIOLOGY. [XXVI. 



and castor oil, clear the sections, and mount them 

 in balsam. 



10. Remove the retina from a fresh eye to osmic acid 

 1 p.c. A/ter a few hours, treat with alcohol. Im- 

 bed and mount the sections in dilute glycerine. 

 In all cases take a small piece for making sec- 

 tions. If long vertical sections are made they 

 are very apt to turn over. 



Examine the two preparations of § 9 and § 10, 

 some points will be best seen in the one, some 

 in the other. Observe the following structures 

 from within (anterior surface) to without (pos- 

 terior surface). 



a. The inner limiting membrane ; from this 

 the fibres of Miiller are seen to start with 

 a broad foot and to run vertically outwards, 

 becoming thinner as they go; they may 

 readily be traced as far as /, and may be 

 followed to the outer limiting membrane (h), 

 here and there anastomosing branches be- 

 tween the neighbouring fibres of Miiller may 

 be seen. 



b. The layer of optic fibres. The nerve- 

 fibres here are without medullary sheaths, or 

 rarely possess them. 



c. The ganglionic layer; this consists of a 

 single layer of large nerve-cells with con- 

 spicuous nuclei. Externally a single process 

 may be seen running into the optic fibre 



' layer, internally several processes branching 

 into 



