the walls of the bladder have not been ruptured. I mention this because
Cohn quotes a statement by Treviranus, that air cannot be forced out of
a bladder without rupturing it. We may therefore conclude that whenever
air is secreted within a bladder already full of water, some water will
be slowly driven out through the orifice. Hence I can hardly doubt that
the numerous glands crowded round the orifice are adapted to absorb
matter from the putrid water, which will occasionally escape from
bladders including decayed animals.
[In order to test this conclusion, I experimented with various
solutions on the glands. As in the case of the quadrifids, salts of
ammonia were tried, since these are generated by the final decay of
animal matter under water. Unfortunately the glands cannot be carefully
examined whilst attached to the bladders in their entire state. Their
summits, therefore, including the valve, collar, and antenn , were
sliced off, and the condition of the glands observed; they were then
irrigated, whilst beneath a covering glass, with the solutions, and
after a time re-examined with the same power as before, namely No. 8 of
Hartnack. The following experiments were thus made.
As a control experiment solutions of one part of white sugar and of one
part of gum to 218 of water were first used, to see whether these
produced any change in the glands. It was also necessary to observe
whether the glands were affected by the summits of the bladders having
been cut off. The summits of four were thus tried; one being examined
after 2 hrs. 30 m., and the other three after 23 hrs.; but there was no
marked change in the glands of any of them.
Two summits bearing quite colourless glands were irrigated with a
solution of carbonate of ammonia of the same strength (viz. one part to
218 of water) , and in 5 m. the primordial utricles of most of the
glands were somewhat contracted; they were also thickened in specks or
patches, and had assumed a pale [page 419] brown tint. When looked at
again after 1 hr. 30 m., most of them presented a somewhat different
appearance. A third specimen was treated with a weaker solution of one
part of the carbonate to 437 of water, and after 1 hr. the glands were
pale brown and contained numerous granules.
Four summits were irrigated with a solution of one part of nitrate of
ammonia to 437 of water. One was examined after 15 m., and the glands
357