PHYSIOLOGY OF PEPSIN-FORMING GLANDS. 
703 
into the stomach of the Frog ; but the results, although on the whole favourable to 
the view that peptone causes a secretion, yet present some exceptions which prevent 
my forming any decided opinion on the subject. 
The increase of granules and the growth of the cell during the last hours of digestion 
is in all probability due to the presence of the assimilated products of digestion. 
In a worm-fed Frog, from the eighth to the eighteenth hour the secretion is going 
on at least as rapidly as in a sponge-fed animal, and yet the granules increase in number 
in the cells. We have seen reason to think that the first absorbed products cause an 
increased using up of granules, so that during the eighth to the eighteenth hour of 
digestion there must be some additional factor causing the formation of granules. It 
seems to me most likely that this additional factor is the presence of some of the 
digestive products which have been converted into a fit state to be assimilated by the 
gland-cells. 
The effect of digestible substances in increasing the rate of growth of the cells and 
the formation of granules is strikingly shown in such an experiment as the following. 
Three Frogs are fed with sponge. In twenty-four hours the sponge is removed 
from two of these Frogs ; one of the two is fed with worm. All three are killed in 
twenty-four hours more, and the oesophageal glands examined. We have, then, 
specimens of glands from Frogs all forty-eight hours from the time of feeding with 
sponge, but (1) has been stimulated by the sponge during the whole time, (2) has 
been stimulated during the first twenty-four hours only, (3) during the first twenty- 
four hours with sponge, during the last twenty-four hours with worm. 
Now, it is found that the gland-cells of (1) are small and contain very few granules, 
whilst those of (3) are large and contain many granules ; yet the gland-cells of (3) 
have poured forth at least as much and probably more secretion than those of (1), i.e., 
at least as many granules have been used up in (3) as in (l), and yet (3) contains very 
many more granules. 
Further, the size of the cells and the number of the granules is not very different 
in (2) and (3), i.e., the gland-cells of (2) which have used up no granules during the 
twenty-four hours before examination are not more granular than those of (3), in 
which a very considerable using up of granules has taken place. 
We see from (2) that when the stimulus is removed the cells form granules, although 
no digestive products have been absorbed ; the more rapid formation of granules which 
takes place when digestible substance is given I attribute to an increased supply of 
those substances which serve as food to the cells. 
The same conclusion results from comparing the effects of sponge and of worm¬ 
feeding on Triton tceniatus. The details of such experiments are given above ; it is 
unnecessary to discuss them here. 
