MUCUS. 55 



logous secretion is produced by the mucous membrane of 

 the pharynx and oesophagus. 1 During the intervals of di- 

 gestion, a viscid, alkaline secretion covers the mucous mem- 

 brane of the stomach. The digestive secretions of the small 

 intestine are so viscid that it has been found impossible to 

 separate them from the true mucous secretion ; but un- 

 doubtedly a secretion of ordinary mucus is constantly taking 

 place from the lining membrane of both the small and the 

 large intestine. This secretion probably has a purely me- 

 chanical function, serving to lubricate the membranes and 

 facilitate the movements of the opposing surfaces against 

 each other. 



The mucous membrane of the gall-bladder produces quite 

 an abundant secretion ; but this is always mixed with the 

 bile, and will be considered in connection with the composi- 

 tion of this fluid, though it is not known to possess any pe- 

 culiar properties. 



Mucus of the Urinary Passages. A small quantity of 

 mucus is secreted by the urinary passages. This is present 

 in the normal urine, in the form of a very slight, cloudy de- 

 posit, which forms after the urine has been allowed to stand 

 for a few hours. A certain amount of secretion takes place 

 from the mucous membrane of the bladder, which, as we 

 have seen, does not possess glands except near the neck. 

 This secretion takes place in very small quantity, and may 

 be recognized in the urine by the ordinary microscopical 

 characters of mucus. 



Jfu-cus of the Generative Passages. The vagina secretes 

 a small quantity of mucus, which differs from the secretions 

 of the other mucous membranes in being distinctly acid and 

 almost entirely wanting in viscidity. The mucus of the 

 neck of the uterus is clear, viscid, and distinctly alkaline. 

 This is ordinarily produced in small quantity, but is very 



1 See vol. ii., Digestion, p. 166. 



