HISTOLOGICAL DEMONSTRATIONS. 131 



hour or so in a J per cent solution of gold chloride, and 

 after thorough washing in water, and exposure to diffuse 

 light for two days in water slightly acidulated with acetic 

 acid, it will be found that on teasing out a small piece of 

 the retina the outer segments of the rods readily tend to 

 cleave transversely. 



d. To make good sections of the retina has hitherto 

 been a matter of the greatest difficulty, for any imbedding 

 agent that may be used is so apt to spoil the bacillary layer. 

 The freezing microtome has, however, overcome the difficulty 

 completely, and it is easy to obtain any number of perfect 

 sections with its aid. 



240. Structure (H.) V. S. retina of cat prepared as 

 stated in 239, a. Place the ends of the section towards 

 the ends of the slide, add a drop of Farrants' solution. 

 Cover, and examine. 



The general scheme of the structure of the retina is this 

 (Schultze) : Delicate nervous elements are supported by 

 a framework of connective tissue. The rods and cones are 

 the terminations of the fibres of the optic nerve with which 

 their connection is probably the following. A nerve fibril 

 passes from the inner segment of each rod, and has one or 

 two nuclear swellings upon its course inwards. From the 

 inner segment of each cone there passes a bundle of fibrils, 

 which has also at least one nuclear swelling upon its course 

 inwards. Both the rod and cone fibrils join multipolar 

 nerve cells at the inner part of the retina, which in turn 

 are connected with the fibres of the optic nerve. The 

 actual continuity of the rod and cone fibrils with the 

 multipolar nerve cells has not, however, been traced as yet. 



The connective tissue elements principally consist of a 

 membrane (inner limiting membrane] on the inner aspect of 

 the retina, and another (outer limiting membrane) inside the 

 rods and cones, with trabeculae (fibres of Muller) passing 

 between the two. Nine or even ten layers may be dis- 

 tinguished in the retina which we have now to examine in 

 detail in the preparation. 



i. Inner limiting membrane, with the fibres of Muller 

 extending from it outwards. 



