SECRETION OF SALIVA AND GASTRIC JUICE. 269 



watched under the microscope. The vascular changes can, of course, be 

 easily appreciated, but the granules may also be seen to diminish in number. 

 Those at the inner margin seem to be discharged into the lumen, and those 

 nearer the outer margin to travel inward through the cell-substance toward 

 the lumen, the faint striae spoken of above, apparently, at all events, being 

 the marks of their paths. Obviously, during secretion, the granules with 

 whicli the cell-substance was " loaded " are " discharged " from the cell into 

 the lumen of the alveolus. What changes these granules may undergo dur- 

 ing the discharge we shall consider presently. 



Sections of the prepared and hardened pancreas of any animal tell nearly 

 the same tale as that thus told by the living pancreas of the rabbit. In 

 sections, for instance, of the pancreas of a dog which has not been fed, and 

 therefore has not been digesting, for some hours (twenty-four or thirty), the 

 cells are seen to be crowded with granules (which, however, are usually 

 shrunken and irregular owing to the influence of the hardening agent), 

 leaving a very narrow outer zone. In similar sections of the pancreas of a 

 dog which has been recently fed, six hours before for example, and in which, 

 therefore, the gland has been for some time actively secreting, the granules 

 are far less numerous, and the clear outer zone accordingly much broader 

 and more conspicuous. With osmic acid these granules stain well, and are 

 preserved in their spherical form, so that the cell thus stained maintains 

 much of the appearance of a living cell. But with carmine, hsematoxylin, 

 etc., the granules do not stain nearly so readily as does the cell-substance of 

 the cells, so that a discharged cell stains more deeply than does a loaded cell 

 because the staining of the " protoplasmic " cell-substance is not so much 

 obscured by the unstained granules ; besides which, however, the actual cell- 

 substance stains probably somewhat more deeply in the discharged cell. It 

 may be added that in the discharged cell the nucleus is conspicuous and well 

 formed ; in the loaded cell it is generally in prepared sections, more or less 

 irregular, possibly because in these it is less dense and more watery than in 

 the discharged cell, and so shrinks under the influence of the reagents 

 employed. 



These several observations suggest the conclusion that in a gland at rest 

 the cell is occupied in forming by means of the metabolism of its cell-sub- 

 stance and lodging in itself ( 30) certain granules of peculiar substance 

 intended to be a part and probably an important part of the secretion. 

 This goes on until the cell is more or less completely " loaded." In such a 

 cell the amount of actual living cell-substance is relatively small, its place 

 is largely occupied by granules, and in itself has been partly consumed in 

 forming 'the granules. During the act of secretion the granules are dis- 

 charged to form part of the secretion, other matters, including water, as we 

 shall see, making up the whole secretion ; and the cell would be proportion- 

 ately reduced in size were it not that the act of the discharge seems to stimu- 

 late the cell-substance to a new activity of growth, so that the new cell-sub- 

 stance is formed ; this, however, is in turn soon in part consumed in order to 

 form new granules. And what is thus seen with considerable distinctness 

 and ease in the pancreas, is seen with more or less distinctness in other 

 glands. 



204. When we study an albuminous gland, the parotid gland, for in- 

 stance, in a living state, we find that the changes which take place during 

 activity are quite comparable to those of the pancreas. During rest (Fig. 

 83, JL), the cells are large, their outlines very indistinct, in fact almost in- 

 visible, and the cell-substance is studded with granules. During activity 

 (Fig. 83, J5) the cells become smaller, their outlines more distinct, and the 

 granules disappear, especially from the outer portions of each cell. After 



