every where alike as to its external charac- 

 ter, but in other respects, it varies very much in 

 its chemical properties, according to the different 

 nature of the substances with which it is destined 

 to come in contact* I have, myself, found in an 

 experiment I made on the mucus, that it has cer- 

 tain varying chemical characters in the nose, in 

 the trachea, in the gall bladder, in the urinary 

 bladder, and in the bowels, without which it could 

 not answer its destined purposes. The mucus, 

 in the nature of its composition, is not a solution ; 

 but contains a solid body, which has the property 

 of swelling in water and becoming a tough half- 

 liquid mass, which, however, is not dissolved if 

 more water is added, and which may be deprived 

 of its w ater, by placing it on blotting paper, and 

 thereby rendered more dense. The humour by 

 which the mucus is penetrated is nothing else than 

 serum, which, however, has lost almost its whole 

 portion of albumen, retaining only the other consti- 

 tuent parts. The peculiar substance, which forms 

 the mass of the mucus, for instance, in the nose, 

 is soluble both in acids and in alkalies, although 

 somewhat more slowly in the latter ; but, on the 

 contrary, it is very easily dissolved, in the gall- 

 bladder, by means of alkali ; but is completely 

 precipitated by acids. By this property, the mucus 



