368 CHAPTER XXVIII. 



saturated aqueous solution of picric acid, and dehydrate for 

 thirty seconds in alcohol containing 0'5 per cent, of picric 



acid. 



3. Hsemalum for two hours, neutral orcein as above for 



ten to twenty minutes. 



657. Horn, Hair, and Nails. The elements of hairs and 

 nails may be isolated by prolonged maceration in 40 per 

 cent, potash solution, or by heating with concentrated sul- 

 phuric acid. See also VON NATHUSIUS, Zool. Anz., xv, 1892, 



p. 395. 



Horny tissues stain well in safranin or gentian violet 

 (REINKE, Arch. f. mik. Anat., xxx, 1887, p. 183 ; ERNST, ibid., 

 xlvii, 1896, p. 669; RABL, ibid., xlviii, 1896, p. 489). 



658. Skin-nerves and Nerve-endings. Impregnate with gold 

 chloride. See previous editions, and the methods given in 

 Chap. XVIII. 



659. Tactile Corpuscles. FISCHER (Arch. f. mik. Anat., 

 1875, p. 366) employed the gold method of Lowit see 

 351. RAN VIE R (Traite, p. 918) also recommends this 

 method, as well as his two gold methods, 352, 353. See 

 RANVIEE, Traitv, p. 919; LANGERHANS, Arch.f. mik. Anat., 

 1873, p. 730; KULTSCHIZKY, ibid., 1884, p. 358; and 

 SMIRNOW, Intern. Monatsschr. f. Anat., etc., x, 1893, 6, 

 p. 241 ; Zeit. f. wiss. Mik., x, 2, 1893, p. 254 (this observer 

 recommends, beside the gold method of Lowit, the rapid 

 bichromate of silver method of Grolgi). 



660. Corpuscles of Herbst and Corpuscles of Grandry. DOGIEL 

 (Arch.f. Anat. .u. EntwickeL, 1891, p. 182 ; Zeit.f. wiss. Mik., 

 viii, 4, 1892, p. 520) prefers the methylen blue method 

 (Chap. XVII). Four per cent, solution of methylen blue, 

 warmed to 40 C., is injected into blood-vessels of the heads 

 of ducks or geese ; pieces of skin are removed from the 

 beaks, sectioned in pith, and the sections brought on to 

 slides and moistened with aqueous or vitreous humour from 

 the animal, and left for a few minutes exposed to the air (it 

 is well to add to the aqueous or vitreous humour a few 

 drops of y'-g- per cent, methylen blue solution). After about 

 ten to thirty minutes the nerve-endings are seen to be stained, 



