704 
MR. J. N. LANGLEY ON THE HISTOLOGY AND 
The differences in the changes produced by secretion in different gland-cells is due 
'partly to variations in the relative rates with ivhich the using up of granules, the 
growth of protoplasm, and the formation of granules go on both in each cell as a whole 
and in various parts of it; partly also to variations in the power of the gland-cells to 
move the granules towards the lumen. 
We have seen that in any one form of cell the three processes go on at different 
rates at different periods of secretion. We should bed priori inclined to conclude that 
they would go on at different relative rates in the gland-cells of different animals. A 
comparison of the extent of the changes during activity presented by the gastric 
glands of Triton tceniatus an.d those of Triton cristatus makes this conclusion, I think, 
necessary. 
If a Newt of each species be taken and each fed with an amount of worm sufficient 
to moderately distend the stomach, the apparent using up of granules is much greater 
in the gastric glands of Triton tceniatus than in those of Triton cristatus. But we 
have no reason to think that one has secreted proportionately more gastric juice than 
the other, that is to say (see above, p. 698), we have no reason to think that one has 
used up more granules than the other. 
Since, however, we observe a marked difference in the total loss, and know further 
that in both the loss as it goes on is partially replaced, the conclusion naturally follows 
that in one the replacement is more active than in the other, i.e., that the com¬ 
paratively slight change observed in the gland-cells of Triton cristatus is due to the 
formative processes going on at a rate closely corresponding with that of the excretory 
processes. The effect of sponge feeding in the two species of Newts also leads to the 
same conclusion. In both cases an acid secretion of good digestive power is obtained, 
but the observable diminution in the number of granules in the cells is very small in 
the one compared with the diminution observed in the other. 
But although variations of this kind may serve to explain certain of the differences 
which we find in the behaviour of the gland-cells of different animals, they still leave 
a great deal to be explained. Why do some cells form a non-granular zone at their 
outer border, others at their inner border, whilst others again form no non-granular 
zone at all ? 
We may attempt to explain these differences, still having recourse to the three 
main changes which we have seen take place in all the cells. We may suppose that 
these three processes proceed at unequal rates in the outer and inner portions of the 
cells. Obviously a non-granular region might be formed in any part of a cell either 
by a more rapid using up of granules, or by a more rapid growth of protoplasm in 
that part. 
I shall not here discuss the cause of the non-granular border which is formed in 
the inner portion of cells, such as those of the gastric glands of Frogs. For although 
