426 THE SALIVARY GLANDS, BY E. F. W. PFLUGER. 



membrana propria they still hang together in small groups. It 

 is noteworthy in regard to the size of the epithelial cells, that 

 as a general rule those contained in the same alveolus are of 

 nearly the same size. But if we compare those belonging to 

 different alveoli, they are found to be of very different dimensions. 

 It is possible that the small epithelial cells may belong to 

 alveoli of smaller diameter. There may, however, be found all 

 the transitional forms between the two, so that we are here 

 dealing only with the same gland substance in different stages 

 of development. This remark applies also to adult animals. 



If we now proceed to examine with more minuteness the 

 salivary cells of the alveoli, I must in the first place observe 

 that they appear to be invested by a membrane both towards 

 the lumen of the tube and where they are in apposition with 

 each other. It is important to observe that the double con- 

 tours of two salivary cells in contact with one another, are 

 not always perfectly distinct, as though at some points there 

 existed a still more intimate union between them. The proto- 

 plasm of the salivary cells is tenacious, finely granular, and 

 frequently striated. A cell of this kind may give rise to the 

 impression that its protoplasm is composed of innumerable 

 extremely fine fibrils. The average size of the salivary cells 

 is O014 millimeter in diameter. The largest epithelia of this 

 kind with which I am acquainted, I have found in certain 

 alveoli of the salivary glands of the Ox. 



An extremely pale spherical nucleus is to be found in the in- 

 terior of the protoplasm in all fresh specimens, and even in those 

 that have been moistened with diluted acids. After the action of 

 the acid has been long continued, it becomes highly refractile, 

 and presents a dark and sometimes double contour line. It 

 then gradually shrinks, and applies itself as a flat disk to the 

 wall of the cell, which frequently renders its recognition a 

 matter of difficulty. The cell nucleus lies eccentrically to the 

 salivary cell and alveolus, and immediately beneath the mem- 

 brana propria. Its average size in the fresh condition, after being 

 brought into view by dilute acids, amounts to 0'306 millimeter. 

 The most remarkable peculiarity presented by the nuclei of the 

 cells, when fresh, is that they give off an extremely delicate fibre 

 (fig. 75), which often penetrates that surface of the salivary cell 



