48 R. R. BENSLEY 



It must not be supposed that the technical difficulties of study- 

 ing this intracellular product are wholly overcome by the 

 method just described. When the material is large in amount 

 the method is A-ery satisfactory, but the intensity of the proto- 

 plasmic staining is not sufficient to define the material sharply 

 when it is small in amount. Under these circumstances, a brief 

 mordanting of the section, before staining, in a fresh solution of 

 ammonium stannic chloride will improve the contrast staining, 

 but will detract greatly from the transparency and beauty of the 

 preparation. 



The examination of the sections of the experimental series re- 

 ferred to above, and of a number of normal glands from animals 

 killed as soon as obtained, reveals the presence in all, although 

 in highly variable amounts in the individual members of the 

 series, of a new secretion antecedent. This substance is in the 

 form of vacuoles, occurring exclusively in the outer pole of the 

 cell, which contain a dilute solution similar in its properties to the 

 colloid of the follicular lumen, differing from the latter only in 

 density. There are even in this substance clear vacuoles due to 

 shrinkage in fixation, like those seen in the colloid of the lumen. 



In two members of the experimental series, this substance is 

 present in such amount that it fills quite half the cell. In these 

 cases the cell presents an appearance comparable to that of the 

 secreting cells of an exocrine gland like the pancreas, with the 

 exception that the hylogens are in dilute solution in fairly large 

 vacuoles instead of in the form of granules, and they are in the 

 basal end of the cell instead of the free end. In other words 

 these cells exhibit the ordinary picture of a secreting cell with 

 stored secretion antecedents, but with reversed polarity. 



Figure 1 shows an acinus from one of these glands. The cells 

 are cylindrical in shape with a spherical nucleus placed rather 

 nearer to the free end of the cell than to the base. The base of 

 the cell is filled with sky-blue stained material contained in 

 vacuoles separated from one another by thin sheets of cytoplasm 

 containing mitochondrial filaments. The free pole of the cell 

 directed towards the lumen is finely granular and stained a 

 bluish-pink color. It contains none of the blue staining vacuolar 



