are formed by lamellae, which, according to Claparede, are
diverticula from the oesophagus. {24} These lamellae are coated
with a pulpy cellular layer, with the outer cells lying free in
infinite numbers. If one of these glands is punctured and
squeezed, a quantity of white pulpy matter exudes, consisting of
these free cells. They are minute, and vary in diameter from 2 to
6 microns. They contain in their centres a little excessively fine
granular matter; but they look so like oil globules that Claparede
and others at first treated them with ether. This produces no
effect; but they are quickly dissolved with effervescence in acetic
acid, and when oxalate of ammonia is added to the solution a white
precipitate is thrown down. We may therefore conclude that they
contain carbonate of lime. If the cells are immersed in a very
little acid, they become more transparent, look like ghosts, and
are soon lost to view; but if much acid is added, they disappear
instantly. After a very large number have been dissolved, a
flocculent residue is left, which apparently consists of the
delicate ruptured cell-walls. In the two posterior pairs of glands
the carbonate of lime contained in the cells occasionally
aggregates into small rhombic crystals or into concretions, which
lie between the lamellae; but I have seen only one case, and
Claparede only a very few such cases.

The two anterior glands differ a little in shape from the four
posterior ones, by being more oval. They differ also conspicuously
in generally containing several small, or two or three larger, or a
single very large concretion of carbonate of lime, as much as 1.5
mm. in diameter. When a gland includes only a few very small
concretions, or, as sometimes happens, none at all, it is easily
overlooked. The large concretions are round or oval, and