76 THE SECRETIONS: 



Consequently Berzelius found no fat, but he detected traces 

 of albumen. 



The foregoing remarks refer especially to the mucus of the 

 nostrils and lungs, but as the physico-chemical properties of all 

 sorts of mucus are not quite the same, I shall briefly commu- 

 nicate my own observations and those of Berzelius on the 

 different varieties of mucus. 



1. Nasal mucus. 



Nasal mucus generally occurs as a gelatinous or fibrous, and 

 nearly transparent mass ; after complete evaporation it remains 

 in the basin as a yellow, and tolerably transparent coating. It 

 contains epithelium cells and a few mucus-corpuscles, is not 

 soluble in water, but if it remains in contact with that fluid for 

 a considerable time it yields some mucin, in consequence of 

 which the addition of acetic acid to the water produces a 

 very slight turbidity. When water containing mucus is sub- 

 mitted to filtration, the latter remains on the filter and gra- 

 dually solidifies. Berzelius has observed that it may be dried 

 and again diffused through water repeatedly, without changing 

 its properties ; it ultimately, however, becomes opaque, yellow, 

 and apparently purulent. When boiled with water it does not 

 shrivel and harden, but only slightly contracts, and may be 

 diffused by shaking. On cooling, it again becomes tenacious 

 and viscid. By dry distillation of evaporated mucus we obtain 

 carbonate of ammonia and Dippers oil. Mucus dissolves in 

 dilute sulphuric acid ; in the concentrated acid it becomes dark 

 coloured and is decomposed. Dilute nitric acid causes a su- 

 perficial coagulation ; acetic acid induces a degree of contrac- 

 tion, and the mucus does not dissolve in it at a boiling heat. 

 On the addition of caustic alkalies, it, at first, becomes tough 

 and thick, but subsequently dissolves into a thin fluid. 



2. Bronchial and pulmonary mucus. 



These are very similar to nasal mucus. They separate into 

 clear and gelatinous, or else into gray or yellowish flocculi, 

 which remain suspended in water for some time, but ultimately 

 sink to the bottom. 



