70 MUCUS-CORPUSCLES. 
3. Mucus-corpuscles. The mucus corpuscles have already 
been described as cells, in consequence of their resemblance to 
the ceils of epithelium. They are round globules, enclosing a 
nucleus, which is eccentrical. We already know this to be 
the elementary form of most animal and vegetable cells, and 
the presence and characteristic position of the nucleus, there- 
fore, warrant us in concluding that in this imstance also the 
globule is a cell, although an especial cell-membrane cannot 
be distinguished. Giiterbock discovered that the nucleus of 
the mucus-corpuscle has the peculiar property of splitting into 
two or three smaller corpuscles when acted upon by acetic 
acid, and that the enclosing or cell-membrane is gradually 
dissolved in the same acid. Vogel, indeed, attributes this pro- 
perty to such mucus-corpuscles alone as have been secreted 
by a morbid action, and to pus-corpuscles. But I have been 
informed by Henle that the true mucus-corpuscles (of which, 
according to him, only a very small quantity exist in healthy 
mucus,) exhibit the same peculiarity, and that those which are 
not affected by the acid are true epithelial cells. As I have 
never observed any other cell-nuclei to be similarly acted on 
by acetic acid, the fact marks the distinction between mucus 
and pus-corpuscles and all other cells, and, according to Henle, 
even the youngest epithelial cells do not possess this property, 
so that the mucus-corpuscles differ distinctly from them. It 
appears to be a characteristic of all cell-nuclei that they not 
only are insoluble, but do not even become transparent in 
dilute acetic acid. These, therefore, are peculiar cells, which 
are formed in the fluid of mucus as their cytoblastema, in the 
same manner as the yelk-cells in the fluid of the yelk-ball. 
They become more abundant, when the cytoblastema obtains 
a greater degree of “ plasticity,” as the result of irritation of 
the mucous membrane; and as on the other hand the secretions 
in the normal condition possess but a very small amount of 
plastic force, and some—the urine and bile, for instance— 
have not any; we accordingly find in them but a very few 
cells, or indeed none at all, save some cast-off epithelium. I 
have not investigated the question whether the nucleus exist 
before the cell in the mucus-corpuscles, or upon what the 
division of these nuclei by means of acetic acid depends. 
