COMPOUNDS OF ORGANIZATION. 61 



when the boiling is discontinued, it is found collected again 

 at the bottom of the vessel, and nearly as mucous as before. 

 I should observe, however, that this mucus naturally con- 

 tains a little albumen, which must first be extracted by cold 

 water, to enable the remaining mucus to exhibit the above 

 mentioned appearances. The nasal mucous matter dissolves 

 in diluted sulphuric acid ; when the acid is concentrated, 

 the mucus is carbonized. Nitric acid at first coagulates it, 

 a number of yellow spots being dispersed through the coa- 

 gulum ; but by continuing the digestion it softens, and it 

 finally dissolves into a clear yellow liquid, containing none 

 of that yellow substance which I have described under 

 Fibrin. 



" Acetous acid hardens mucous matter, but without dis- 

 solving it, even in a boiling heat. Caustic alkali, at first, 

 renders mucous matter more viscous, and afterwards dis- 

 solves it into a limpid flowing liquid. Tannin coagulates 

 mucus, both when softened by the absorption of water, and 

 when dissolved either in an acid or an alkali." 



This substance occurs in a liquid state in the animal eco- 

 nomy, as a protecting covering to different organs. It ne- 

 cessarily differs in its qualities, according to the purposes it 

 is destined to serve. In the nose, it defends the organ of 

 smell from the drying influence of the air, in the bladder, 

 it protects the interior from the contact of the acid urine, 

 while it preserves the gall-bladder from the action of alka- 

 line bile. It does not contain any suspended particles like 

 the blood, but is homogeneous *. When inspissated, it con- 

 stitutes, in the opinion of some, the basis of the epidermis, 

 horns, nails, feathers. But the difficulty of obtaining it in 

 a pure state, and the discordant characters assigned to it by 

 different chemists, prevent us from reposing confidence in 



* Dr YOUNG, Annals of Fhil. ii. p. 11T. 



t 2 



