52 SECRETION. 



Examined by the microscope, in addition to the mixture of 

 epithelium and occasional leucocytes, which give to the fluid 

 its semiopaque character, the mass of the secretion presents, a 

 very finely striated appearance, as though it were composed 

 of thin layers of a nearly transparent substance, with many 

 folds. These delicate striae do not usually interlace with 

 each other, and are rendered more distinct by the action of 

 acetic acid. This appearance, with the peculiar effect of 

 the acid, is characteristic of mucus. Some varieties of mu- 

 cus present very fine, pale granulations and a few small glob- 

 ules of oil. 



On the addition of water, mucus is somewhat swollen, 

 but is not dissolved. An exception to this is the secretion 

 of the conjunctival mucous membrane, which is coagulated 

 on the addition of water. 



As a rule, the reaction of mucus is alkaline ; the only 

 exception to this being the vaginal mucus, which is very 

 fluid and distinctly acid. 



It is exceedingly difficult to get an exact idea of the prox- 

 imate composition of normal mucus, from the fact that the 

 quantity secreted by the membranes in their natural condi- 

 tion is very small, being just sufficient to lubricate their 

 surface. All varieties, however, contain a peculiar organic 

 principle, called mucosine, which gives the fluid its peculiar 

 viscidity They likewise present a considerable variety of 

 inorganic salts ; as the chlorides of sodium and potassium, 

 alkaline lactates, carbonate of soda, phosphate of lime, a 

 small proportion of the sulphates, and, in some varieties, 

 traces of iron and silica. 1 



Of all these constituents, mucosine is the most important, 

 as it gives to the secretion its characteristic properties. Like 

 all other organic nitrogenized principles, mucosine is coagula- 

 ble by various reagents. It is imperfectly coagulated by heat ; 

 and after desiccation can be made to assume its peculiar con- 



1 SIMON, Animal Chemistry with reference to the PJiysiology and Pathology of 

 Man, Philadelphia, 1846, p. 351. 



