wing method is still better. The preparation is placed in a
closed vessel containing iodine crystals. Within a few minutes it takes
on a dark brown colour, and is then mounted in a saturated laevulose
solution, whose index of refraction is very high. To preserve these
specimens they must be surrounded with some kind of cover-glass cement.

By the use of better methods the red blood corpuscles which have taken
on the iodine stain stand out, without having undergone any
morphological change. The white blood corpuscles are only slightly
stained. All parts containing glycogen on the contrary, whether the
glycogen be in the white blood corpuscles, or extracellular, are
characterised by a beautiful mahogany brown colour. The second
modification of this method is specially to be recommended on account of
the strong clearing action of the laevulose syrup. In using the
iodine-indiarubber solution a small quantity of glycogen in the cells
may escape observation owing to the opaqueness of the indiarubber, and
occasionally too by the separate staining of the same. The second more
delicate method is for this reason recommended, in the investigation of
cases of diabetes and other diseases[7].

2. The microscopic test of the distribution of alkali in the blood.

These methods rest on a procedure of Mylius for the estimation of the
amount of alkali in glass. Iodine-eosine is a red compound easily
soluble in water, which is not soluble in ether, chloroform, or toluol.
But the free coloured acid, which is precipitated by acidifying
solutions of the salt, is very sparingly soluble in water. It is, on the
contrary, very easily soluble in organic solvents, so that by shaking,
it completely passes over into an etherial solution, which becomes
yellow. If this solution be allowed to fall on glass, on which deposits
of alkali have been formed by decomposition, they stand out in a fine
red colour as the result of the production of the deeply coloured salt.

In its application to the blood, of course the vessels used for staining
as well as the cover-glasses must be cleaned from all adhering traces of
alkali by means of acids. The dry specimen is thrown directly after its
preparation into a glass vessel containing a chloroform or
chloroform-toluol solution of free iodine-eosine. In a short time it
becomes dark red. It is then quickly transferred to another vessel
containing pure chloroform, which is once more changed, and the
preparation still