perty, that they stain in acid and neutral dyes respectively; they
shew a much smaller affinity for the basic dyes. The fact that they
greatly exceed the other elements of the bone-marrow in all classes of
animals, is evidence of the importance of these granules.

The second group of bone-marrow cells contains granules which we find in
the whole vertebrate series from the frog to man, and which therefore
are not characteristic for any one species of animal. They are, (1) the
eosinophil cells, (2) the basophil mast cells.

The bone-marrow forms which are free from =granules= consist mostly of
mononuclear cells of different type. They are not nearly so numerous, or
so important as the granulated kind, more especially as the first and
predominant group.

Amongst the granule-free forms the =giant cells= deserve special mention,
for they are an almost constant constituent of the bone-marrow of the
mammalian class. According to the recent researches of Pugliese the
giant cells are considerably increased after extirpation of the spleen
in the hedgehog; an organ of quite extraordinary size in this animal and
doubtless therefore possessing important haematopoietic functions.

Pugliese asserts that in the hedgehog after splenectomy the nucleated
giant cells pass into leucocytes by amitotic nuclear division.
Unfortunately in his preliminary communication there are no notes of the
granules of the bone-marrow cells.

On examining a stained dry preparation of the bone-marrow of the
guinea-pig, rabbit, man, etc. it is seen that the characteristic finely
granular cells are present in all stages of development, from the
mononuclear through the transitional to the polynuclear (polymorphously
nucleated) forms, which we meet with in the circulating blood. A glance
at a preparation of this kind shews that the bone-marrow is clearly the
factory where typical polynuclear cells are continuously formed from the
granule-containing mononuclears.

Here also the same process of ripening can be seen in the polynuclear
eosinophil leucocytes.

Ehrlich has been able by special differential staining to bring forward
proof that the constitution of the granulation changes during the
metamorphosis of the mononuclear to the polynuclear cells. In the young
granules there is prominent a basophil portion that becomes less and
less marked as the cell grows older. The pseudo-eosinophil granules of
the mononuclear cells, of the guinea-pig for example, stai