PHYSIOLOGY OF PEPSIN-FORMING GLANDS. 
701 
stances the loss may be, though it is not normally, covered during the first one to three 
hours. The number of granules contained by any gland-cell at a given time during 
secretion depends then upon the relative rate of formation and using up of granules. 
(c.) There is, I think, also sufficient evidence to justify us in believing that there is 
a continuous though not uniform growth of protoplasm during activity. The organic 
substances in the fluid secreted are formed, for the most part at any rate, by the cell- 
protoplasm. A growth of cell-protoplasm sufficient to cover the loss of the organic 
substances secreted must then, at some time or other, take place. Does this growth 
take place in “rest” or “activity”? The following consideration will, I think, show 
that although there may be a slight growth in rest, the growth takes place, in the 
main, during activity. With the exception, perhaps, of the oxyntic glands of the 
Snake, all the glands above considered have normally nearly returned to their hungry 
condition by the end of the digestive period, i.e., at the end of twelve to twenty hours 
of secretion. The protoplasm which has been continuously diminishing, owing to the 
continuous formation of zymogen, is hardly appreciably in less quantity than at the 
beginning. The protoplasm, then, has grown during secretion. I know of nothing 
which tends to show that the growth of protoplasm is limited to any particular period 
of digestion ; there are, on the other hand, several facts which go far to prove, if 
indeed they do not prove, that the growth is continuous during digestion. 
In the second stage of digestion the cells increase in size, since we have no reason 
to imagine that the stored-up substances, the zymogen and so forth, occupy a greater- 
space than the protoplasm from which they are formed, we may, I think, fairly refer 
the greater part at any rate of this increase in the size of the cells to a growth of the 
protoplasm ; further, since the cells are during this period still losing substances to the 
fluid secreted, the total growth of protoplasm must be very considerable. 
We have seen that under certain circumstances it may happen that there is a similar 
increase in the size of the cells, i.e., a similar growth of protoplasm in the first one or 
two hours of digestion ; we might then adopt a course of reasoning like that adopted 
in considering the formation of granules, and conclude that the protoplasm is growing 
also in the first stage of digestion when the cells are diminishing in size. We have, 
however, more direct evidence to show that this is the case. 
It is true that the cells diminish in size during this stage of digestion, but they do 
not diminish sufficiently in size to warrant us in supposing that there is no growth of 
protoplasm. The mere extraction of the granules which have disappeared would leave 
the cells very much smaller ; this fact becomes the more striking when we reflect that 
in the meantime more protoplasm has been used up to form granules. The changes 
which take place in the oesophageal glands of the Frog after the animal has been fed 
with sponge will serve as an instance. When the granules have entirely disappeared 
from the cell, is it to be supposed that the cell is simply as it was at the beginning of 
secretion, except that it has lost all its granules and a part of its protoplasm, viz.: that 
