228 PRACTICAL HISTOLOGY [XXIX 



with some vitreous humour still attached to it. A drop or two 

 of '06 p.c. methylene blue in salt solution is added, and it is left 

 for 20 to 40 minutes covered up ; when examination with a low 

 power shows that staining has occurred, the methylene blue 

 is washed off with a little salt solution, and half-a-dozen drops of 

 a saturated solution of ammonium picrate added ; in 3 to 4 hours 

 a drop or two of glycerine and ammonium picrate is added, 

 in 18 to 20 hours the fluid is poured off, and the retina mounted 

 in glycerine and ammonium picrate. 



A little ammonia may be added to the ammonium picrate, 

 and gum and sugar used as mounting agent. 



The retina may be hardened in mercuric chloride for 

 observing the effect of light on the retinal elements. 



