234 THE MICROSCOPE. 



immerse it in glycerine and distilled water, in the 

 proportion of one to two ; lastly, place it in water, 

 and brush gently with a sable pencil to remove 

 any precipitate, when it will be fit for mounting in 

 glycerine. The colour of the cornea should be grey 

 Tiolet. 



Mr. Schafer adopts another method a double chlo- 

 ride of gold and potassium solution. 



Osmic acid, first used by Schultze, is useful for the 

 demonstration of fatty matters, all of which it colours 

 black ; it is also valuable for certain nerve preparations. 

 Specimens should be allowed to remain in a 1-2 per 

 cent, aqueous solution of the acid from a quarter to 

 twenty-four hours, when the staining will be completed ; 

 but if it is desired to harden specimens at the same 

 time, they should remain in it for some few days. Osmic 

 acid does not penetrate very deeply, therefore small 

 portions should be selected for its action. 



Chloride of palladium, another of Schultze's staining 

 fluids, is nsed to stain and harden the retina, crystalline 

 lens, and other tissues of the eye ; the cornified fat and 

 connective tissues remaining uncoloured. The solu- 

 tion should be used very weak : Chloride of palladium, 

 1 part ; distilled water, 1,000 parts. Specimens should 

 be mounted in glycerine at once, or further stained 

 with carmine. 



Schafer also employs a silver nitrate and gelatine 

 solution for demonstrating lung epithelium ; this is 

 made as follows : Take of gelatine 10 grin., soak in 

 cold water, dissolve, and add warm water to lOOc.c. 

 Dissolve a decigramme of nitrate of silver in a little 

 distilled water, and add to the gelatine solution. Inject 

 this with a glass syringe into the lung until distension 

 is pretty complete. Leave it to rest in a cool place 

 until the gelatine has set ; then cut sections as thin as 

 possible, place them on a slide with glycerine, and 

 expose to light nntil ready for mounting. 



Of the double stains Mr. Groves refers only to those 

 where the double colour is produced by a single pro- 

 cess. Those in which one colour is first employed, and 

 then another. Those used as a single fluid are Picro 



