516 LIQUID PARTS OF ANIMALS. 



Brought over, . . 95 



Ehosphate of lime, . . trace. 



95 

 Loss, . 5 



100 



VI. A curious set of experiments has been made by Leopold 

 Gmelin on the black pigment, which lines the choroid coat of 

 the eye. From 500 eyes of oxen and calves he collected 75 

 grains of this substance. Its colour is blackish brown. It is 

 tasteless, and adheres to the tongue like clay. It is insoluble in 

 water, alcohol, ether, oils, lime-water, and distilled vinegar. It 

 dissolves in potash and ammonia when assisted by heat, and is 

 again precipitated by acids. Sulphuric acid dissolves it and ac- 

 quires a black colour. Muriatic acid forms only an imperfect 

 solution. Nitric acid dissolves it, and changes its colour to red- 

 dish-brown. When distilled it yields water, a brown oil, and 

 carbonate of ammonia. It gives out at the same time carburetted 

 hydrogen, carbonic oxide, azotic and oxygen gas. The coal re- 

 maining in the retort consists almost entirely of charcoal. * 



CHAPTER XVIII. 



OF CERUMEN. 



CERUMEN* or ear-wax is a yellow-coloured liquid, secreted by 

 the glands of the auditory canal, which gradually becomes con- 

 crete by exposure to the air. It is intended to lubricate the ca- 

 nal, to keep the parts soft, and to prevent insects from making 

 their way to the tympanum. This secretion was first subjected 

 to a chemical examination by Fourcroy and Vauquelin, who 

 was supplied with a sufficient quantity of serum for the purpose 

 by M. Halle. Fourcroy has stated the result of this examina- 

 tion in his Systems des Connoissances Chimiques.\ In the second 

 volume of Berzelius's Animal Chemistry, published in 1808, he 



* Schweigger's Jour. x. 507. 



f From xgoc, wax, from its resemblance to wax. 



Vol. ix. p. 454 of the English translation. 



