328 SECRETION. 



tough and adhesive that the vessel containing it may be turned 

 upside down without its running out. The mucus of the cervix 

 uteri has a similar firm consistency, so as to block up the cavity 

 of this part of the organ with a semi-solid gelatinous mass. Mucus 

 is at the same time exceedingly smooth and slippery to the touch, 

 so that it lubricates readily the surfaces upon which it is exuded, 

 and facilitates the passage of foreign substances, while it defends 

 the mucus membrane itself from injury. 



The composition of mucus, according to the analyses of Nasse, 1 



is as follows : 



COMPOSITION OF PULMONARY Mucus. 



Water 



Animal matter ......... 



Fat 



Chloride of sodium 



Phosphates of soda and potassa . 



Sulphates " " 



Carbonates " " , 



1000.00 



The animal matter of mucus is insoluble in water ; and conse- 

 quently mucus, when dropped into water, does not mix with it, but 

 is merely broken up by agitation into gelatinous threads and flakes, 

 which subside after a time to the bottom. It is miscible, however, 

 to some extent, with other animal fluids, and may be incorporated 

 with them, so as to become thinner and more dilute. It readily 

 takes on putrefactive changes, and communicates them to other 

 organic substances with which it may be in contact. 



The varieties of mucus found in different parts of the body are 

 probably not identical in composition, but differ a little in the cha- 

 racter of their principal organic ingredient, as well as in the pro- 

 portions of their saline constituents. The function of mucus is for 

 the most part a physical one, viz., to lubricate the mucous surfaces, 

 to defend them from injury, and to facilitate the passage of foreign 

 substances through their cavities. 



2. SEBACEOUS MATTER. The sebaceous matter is distinguished 

 by containing a very large proportion of fatty or oily ingredients. 

 There are three varieties of this secretion met with in the body, 

 viz., one produced by the sebaceous glands of the skin, another 

 by the ceruminous glands of the external auditory meatus, and 

 a third by the Meibomian glands of the eyelid. The sebaceous 



1 Simon's Chemistry of Man, Philada., 1846, p. 352. 



