178 PRACTICAL HISTOLOGY. 



acetic acid or in glycerine. The time of exposure varies 

 with the intensity of the light; from one to two days 

 usually suffice. Mount the stained tissue in glycerine, or 

 in glycerine jelly. The preparations deteriorate however. 



b. Method for the Cornea. The gold method was intro- 

 duced by Cohnheim for staining the nerves of the cornea. 

 The following method, devised by Klein (Monthly Micro- 

 scopical Journ.jVO\. vii. p. 157), gives better results than 

 Cohnheim's in this case. Remove the cornea from a 

 rabbit or guinea-pig within fifteen minutes after death, and 

 place it in J per cent gold solution, from one and a half to 

 two hours in the case of the rabbit, and rather more than 

 an hour in the guinea-pig. Wash in distilled water, and 

 expose to the light in the water for twenty-four or thirty- 

 six hours, the water being changed twice or thrice. Then 

 transfer the cornea to dilute glycerine (pure glycerine i 

 part, distilled water 2 parts) for two or three days. Lastly, 

 place the cornea in water, and gently brush away any pre- 

 cipitate that may have formed; make sections obliquely 

 horizontal or vertical, and mount in glycerine. A cornea 

 so treated is ash-gray or slightly violet. 



331. Chloride of Palladium was introduced by F. F. 

 Schultze for staining non-striped muscle. It renders the 

 fibres brownish yellow. An aqueous solution of i per 

 1000 is employed, to every 2oCC of which a drop of 

 hydrochloric acid is added, in order to preserve it. For 

 staining, three or four days are required. Schultze recom- 

 mends this as a hardening agent for the lens and the 

 retina. Its use as an adjuvant in the carmine staining of 

 nerve tissue hardened in chromic acid has been alluded to 

 in 319. 



332. Osmic Acid. The value of this substance for 

 blackening, more especially medullary substance of nerve 

 and all fatty matter, has been already alluded to in 281, 

 where it has been described under the head of hardening 

 agents, because of its especial value as such. 





