1895.] MICROSCOPICAL JOURNAL. 357 



was mostly from soundings taken by the Challenger 

 expedition, 1876-78, that Radiolarian science was enriched 

 with some four thousand new species unknown previous 

 to their publication in the Challenger reports. 



Microscopical Technique Applied to Histology. — XII. 



[FROM THE FRENCH OF RENE BONEVAL.] 



Continued from Page 268. 



Epidermis. — Take the skin from the tip of the finger 

 and make — 



/Sections. — To get a general view of the layers of the 

 epidermis treat a small piece with alcohol and gum. Cut 

 perpendicular to the surface; picro-carmine, glycerine. 



Eleidin. — A section is stained on the slide by the fol- 

 lowing: picro-carmine, 1 per cent, 1 drop ; distilled water, 

 10 drops. Examine by a low power, and when the grains 

 of eleidin are red add the thin cover. Replace the picro- 

 carmine by a drop of neutral glycerine allowed to pene- 

 trate slowly. This preparation will keep well. To see 

 the eleidin grains disappear, treat another section, colored 

 as described, with acetic acid glycerine. 



Osjnic acid method. — Put a piece of skin 1 mm. square 

 and well freed from subcutaneous tissue, in a few c. c. of 

 1 per cent osmic acid. In 24 hours wash carefully in 

 filtered Avater (12 hours), and harden in gum and alcohol. 

 Sections, perpendicular to the surface, stained or not in 

 alum carmine, will show the diff"erent layers of the epi- 

 dermis with remarkable distinctness. 



Bichromate method. — A piece of skin is left for a month 

 or longer in a large quantity of 2 per cent ammonia bi- 

 chromate (use 200 c. c. of solution to 1 c. square of skin). 

 Wash in a large amount of water for 24 hours, harden in 

 gum and alcohol. Make very thin sections perpendicular 

 to the surface, and mount in carbolic acid water. This 



