Turner, MorpJiology of tJic Avian Dra'm. 109 



The encephalon was removed and the lateral half of one 

 optic lobe and all of the prosencephalon and epencephalon 

 dissected away. What remained was immersed for one 

 hour in a 3 per cent, aqueous solution of potassium bichro- 

 mate. It was then placed in a 3 per cent, solution of the 

 same substance. After reinaining in this fluid for twenty- 

 three hours, the specimen was transferred to a mixture of 

 three parts of a 3 per cent, aqueous solution of potassium 

 bichromate and one part of a i per cent, aqueous solution of 

 osmic acid. After remaining in this medium for twenty-five 

 hours, the specimen was washed in a .75 per cent, aqueous 

 solution of silver nitrate, and then immersed in a i per cent, 

 solution of the same salt. There, protected from the light, 

 it remained eight days. The brain was then transferred to 

 50 per cent, alcohol, after which it was hardened and sec- 

 tioned in the usual manner. Although eveiy precaution was 

 taken to insure success, yet the desired result was not pro- 

 duced; it was impossible for me to decide what had been 

 impregnated, for evidently much was stained that was not 

 nervous, and it was equally evident that not all nerve tracts 

 had been acted upon by the reagent. While still seeking a 

 good fibre stain, I tried overstaining with Professor Her- 

 rick's modification of Grenadier's ha'matoxylon.C) The 

 result was quite satisfactory. The fibers were well differ- 

 entiated, and the nerve cells, although stained quite densely, 

 were not destroyed. 



IV.— HISTOLOGY OF THE DIENCEPHALON AND 

 MESENCEPHALON. 



Third ventricle (Plate VII, Figs. 3, 7; Plate XIV, Figs. 

 II, 13; Plate XV, Figs. 4, 5, 6, 7, S). — In birds the dien- 

 cephalon is small but compact. The third ventricle is the 

 only cavity within it, and is very narrow. This ventricle 



I This consists of Grenacher's heematoxylin to which has been added a trace of 

 corrosive sijbljroate- This stain cannot be used for staining ui toto. 



