Chemico-Physiological Researches. 417 



If we seek to establish for these horny tissues a formula com- 

 parable with that of protein, we may best adopt C^^ Hgg N^ O,-, 

 from which if we subtract protein (C48 Hgg NgOiJ there re- 

 mains H., N 0.3, or the horny material consists of protein 

 + N H3 + 3 6. 



When horn, wool, or hair is dissolved in solution of potash, 

 ammonia is evolved. On decomposing the liquor by sulphuric 

 acid, removing the precipitate by filtration and distilling, a 

 very sensible quantity of acetic acid may be obtained. If the 

 alkaline solution be decomposed by acetic acid, sulphuretted 

 hydrogen is evolved, and a precipitate formed which agrees 

 perfectly with protein in its character and composition ; but 

 if this precipitate be removed and the liquor decomposed 

 by a new quantity of acetic acid, a grayish solid separates 

 which is of a different nature. Its composition, and that of 

 protein from hair or horn, is as follows : — 



100-000 100-000 



The membrane which encloses the albumen and lines the 

 interior of the shell of the egg was found to be also a horny 

 tissue. 



Feathers. 

 This material, which is usually considered as horny, has 

 been found by Dr. Scherer essentially distinct. It contains 

 to the same carbon, hydrogen and nitrogen, an atom less of 

 oxygen than true horn, the formulae expressing the analy- 

 tical results being €43 H39 N- O^. 



Black Pigment of the Eye. 

 This substance, the details of the preparation of which in 

 tlie pure state may be passed over, consists of 



I. II. III. 



Carbon .... 58-273 58-672 57*908 



Hydrogen . . 5-973 5-962 5-817 



Nitrogen . . . 13-768 13-768 13-768 



Oxygen . . . 21-986 21-598 22-50 7 



100-000 100-000 100-000 



Phil. Mag. S. 3. Vol. 20. No. 1 32. May 1 842. 2 F 



