MUCUS. 125 



blance, they contract somewhat under the influence of acetic 

 acid, and are soluble in a concentrated solution of ammonia. 



2nd. The mucus secreted by false mucous membranes, or 

 those which are analogous to the skin, although more or less 

 thick, does not admit of being drawn out into threads, is acid, 

 and in place of spherical globules contains numerous scales 

 of epithelium which differ from true mucous globules in 

 their much larger size, flattened form, and in their irregular 

 and very frequently oval outline : these scales, like the true 

 mucous corpuscles, are nucleated, and the nuclei comport 

 themselves with chemical reagents, in the same manner as 

 the globules of mucus, 



Example : the mucus of the vagina. (See Plate XII. 



fig- 1.) 



3rd. The mucus proceeding from the mixed or transition 

 membranes is sometimes acid, sometimes alkaline, at others 

 neutral, and contains a mixture of true mucus corpuscles and 

 epithelial scales, the relative proportion of each of which 

 varies according to the exact structure of the membrane by 

 which it is furnished. (See Plate XII. fig. 2.) 



These divisions of the mucus into three different kinds, 

 although to some extent artificial as already observed, are yet 

 not without their practical utility. 



The microscopical and chemical characters of mucus like- 

 wise vary much, not merely according to the general organi- 

 zation of the membrane by which it is secreted, but also in 

 accordance with the condition of the membrane itself, with 

 the degree of irritation or inflammation to which it is sub- 

 ject, and with the precise nature of the disorder by which 

 it is affected ; thus, sometimes, the mucus secreted by the 

 lining membrane of the nose is thin and watery, the fluid 

 element being in excess, and at others it is thick and opaque, 

 its solid globular constituents superabounding. Its colour 

 also as well as its consistence exhibits various modifications 

 in pathological states, being sometimes white, greenish or 

 yellow. 



The description of the different forms of epithelial cells 

 alluded to, and which are occasionally encountered in the 



