MUCUS. 73 



Chemical character of mucus. 



The action of chemical reagents on the epithelium cells and 

 mucus-corpuscles may easily be observed under the microscope. 

 The former are not affected by the addition of water or of 

 dilute acids ; they disappear, however, under the influence of 

 caustic alkalies or concentrated acids. According to Gruby, 

 solutions of the ordinary earthy, and metallic salts effect no 

 change on the epithelium cells. The mucus-corpuscles are 

 very differently acted on. Dilute acetic, oxalic, and tartaric 

 acids speedily deprive the capsules of the mucus-corpuscles of 

 their granular appearance. The corpuscles themselves become 

 round and transparent ; the nuclei become apparent, the cap- 

 sules at length disappear, and the nuclei frequently divide into 

 several granular bodies > so that in place of the mucus-corpus- 

 cles previously visible, there are at last only two, three, or 

 more rounded granules to be seen. 



Dilute mineral acids do not produce these changes in the 

 capsule of the mucus-corpuscle, which remains unchanged, as 

 shown by the observations of Giiterbock, Vogel, Gruby, and 

 myself. Dilute, as well as concentrated solutions of the alkalies 

 and their carbonates render the capsules clearer, and ultimately 

 dissolve them. The free fixed alkalies produce these changes 

 more rapidly than their carbonates; free ammonia much less 

 rapidly than free potash. 



The liquid portion of the mucus always exhibits a decidedly 

 alkaline reaction: when examined under the microscope it ap- 

 pears like a clear fluid, in which, with a very good light, a faint 

 granular appearance is perceptible. On the addition of a little 

 water, a decided coagulation may be observed, and an extremely 

 fine granular precipitate is formed. Acetic, and indeed any 

 weak acid produces a similar effect, but the precipitate is more 

 copious, and forms a grayish granular film, sufficiently strong 

 to admit of traction. The free alkalies and their carbonates do 

 not precipitate this fluid. 



It is clear from the preceding observations that mucus is 

 composed of two distinct parts, the cells and the fluid. The 

 viscidity of the secretion evidently pertains to the latter, and 

 the ingredient that gives rise to this property must be contained 



