J. W. GROVES ON SECTIONS OF ANIMAL TISSUES. 243 



demonstration of fatty matters, which are thereby coloured black ; 

 it is also valuable for some nerve preparations, but it is very irri- 

 tating to the mucous membranes of the experimenter, and should be 

 used with caution. 



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 

 stains wdl be complete ; but if it is desired to harden also by its 

 means, they should remain in it for some few days. 



Osmic acid does not penetrate deeply, therefore small portions 

 should be selected for its action. 



Chloride of palladium, also introduced by Schultze, is used to 

 stain and harden the retina, crystalline lens, &c, and other tissues, 

 but cornified fat and connective tissues remain uncoloured. 



Dissolve : — 



Chloride of palladium ... ... 1 part. 



In water ,, ... ... 1,000 parts. 



An ounce of this solution will harden a piece of tissue the size of 

 a bean in two or three days, staining it at the same time a brown or 

 straw colour. Specimens may be mounted in glycerine at once, or 

 may be further stained with carmine. 



Before proceeding to the double stains, it will be well to mention 

 Schafer's silver nitrate and gelatine solution for demonstrating 

 lung epithelium- 

 Take of gelatine 10 grms., 



soak in cold water, dissolve, and add warm water to 100 c.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 until ready for examination. 



Of the double stains I will specially notice only those where the 

 double colour is produced by a single process. Those in which the 

 one colour is first employed, and then the other, I will simply state 

 which is to be used first, as all further particulars have been already 

 given. 



Those which are used in a single fluid are — 



Picro carmine. 



Carmine and Indigo carmine. 



Anilin blue and anilin red. 



