THE LACHRYMAL GLAND 185 



mounted in either serum or physiological salt solution. The 

 refractive index of these granules is much greater than that of 

 the mounting media and consequently the granules stand out 

 clear]3^ In the great majority of tissues examined, practically 

 all cells of both the tubules and the intercalary ducts appear to 

 possess granules. Only rarely are any of these cells seen free 

 from granules. This condition is due to the fact that the few 

 granule-fiee cells are masked by granular cells which may be 

 above or below them as it is impossible to procure fresh tissue 

 sections one cell layer thick. Fresh lachrymal gland tissue 

 consequently appears as a rule to be in an extremely granular 

 stage. It is possible, however, after examinations of numerous 

 glands to make out several phases in the secretory activities of 

 glands although this is much better seen in permanent prepar- 

 ations. These various phases observed in fresh tissue mounted 

 in ox serum may be generally classified into three groups or 

 types. However, every gradation exists between these groups. 

 A. The first type may be termed the granular stage — in the 

 height of granule formation. All cells of both tubules and inter- 

 calary ducts are filled with granules. The alveolus or tubule is 

 easily recognized surrounded by the basal membrane and inter- 

 stitial tissue. The cell boundaries are readily seen. The 

 majority of cells forming the tubules are completely filled with 

 secretory granules. Consequently no clear basal zone is present 

 as is the case in the pancreas. These granules extend from the 

 base of the cell to the summit. So numerous are they that most 

 cells appear to bulge and as a consequence no lumina are seen. 

 These granules obscure for the most part the nucleus of the cell. 

 In many cells, however, the distal half of the nucleus can be 

 seen lying on the base of the cell. The granules vary in size 

 from almost imperceptibly fine structures to granules several 

 micra in diameter. They vary also in their powers of light 

 refractivity — the smaller ones refract light to a much greater 

 degree than do the larger. There is no regularity in the dis- 

 tribution of large and small granules within the cell. They are 

 scattered throughout the cell, appearing at both the base and 

 the summit. Frequently large granules are seen which have 



