1813.] Chemical Properties of Animal Fluids. 383 



dried will again absorb water when immersed in it, and resume 

 its transparency; and this alternate wetting and drying may be 

 repeated an indefinite number of times, but it thus gradually 

 becomes yellowish and more resembling pus. Five parts of 

 recent mucus absorbed by 95 parts of water produce a glairy 

 mass which will not pour from a vessel. When mucus is boiled 

 with water it docs not become horny, nor does it coagulate ; the 

 violent motion of ebullition rends it in pieces, but 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 contains a little albumen, 

 which must first be extracted by cold warer to enable the re- 

 maining 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 dis- 

 persed through the coagulum ; but by continuing the digestion 

 it softens, and is finally dissolved into a clear yellow liquid con- 

 taining none of that yellow substance which I have described 

 under fibrin. 



Acetous acid hardens mucous matter, but without dissolving 

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

 matter more viscous, and afterwards dissolves it into a limpid 

 flowing liquid. Tannin coagulate- mucus, both when softened 

 by the absorption of water, and when dissolved either in an acid 

 or an alkali. 



The Mucus of the Trachea, as far as I have been able to 

 examine, possesses the same properties with the preceding. The 

 first morning expectoration often contains bluish or dark coloured 

 flocculi, which will imbibe •_:() times their bulk of water, and 

 sometimes become thereby so perfectly transparent as hardly to 

 be distinguished in the surrounding water. Acids and alkalies 

 act upon then us on i asal mucus. 



The M tcu oj the GaU-blud r much resembles that of the 

 nostrils, but is more transparent, and is always tinged yellow by 

 the bile. When dried it will again soften in water, but loses 

 part of its mucous property. BiJi.iry mucus dissolves in alkali, 

 and if> fluidity increases in proportion to the quantity of the 

 Utter. If this solution is exactly saturated with an acid, the 

 mixture becomes slightly turbid, and of a consistence to be 

 dri "• i out ii 1 breads. All the acids produce with biliary mucus 

 a yellow ralum that reddens litmus. The coagulum formed 



wi;l. the sulphuric afcid may be restored to its mucous properties 

 b) exact saturation with an alkali. Alcohol coagulates this 

 D1UCUS into a very yellow granular nia<s, to which the mucous 

 p operty cannot hi- restored. A similar mass is often found in 

 the adipocirous biliary concretion-- ; ttld it is remarkable that it 



