not polymorphous, but usually divided into two, though it may
be single. The cells probably corresponding to _eosinophile_ leucocytes
have fine coccal-shaped granules, faintly staining eosinophile or
neutrophile. The basophile granules of the "mast" cells are
coccal-shaped, of various size--often quite powdery.

_Pigeon._--_Red cells_ resemble those of the fowl, and similar varieties
of appearance may be noted. The granules of those cells which correspond
to _polymorphonuclear_ leucocytes are rod-shaped, but smaller and finer
than in the fowl, and do not show clubbed appearances. The nucleus is
not polymorphous, and only occasionally divided. The coccal-shaped
granules of the _eosinophile_ cells are stained more deeply oxyphile
than those of the corresponding cells of the fowl.

_The preparation of dried films_ for this histological examination of
the blood is carried out as follows:

1. Small samples of blood for the preparation of blood films are most
conveniently obtained from the veins of the ear in most of the ordinary
laboratory animals, viz., monkey, goat, dog, cat, rabbit, guinea-pig; in
the pigeon and fowl the axillary vein should be punctured; in the rat
and mouse either a vein in the ear or preferably by wounding the tip of
the tail; in the frog, the web of the foot should be selected.

2. Puncture the selected vein with a sharp needle. A flat Hagedorn
needle (size No. 8) with a cutting edge is the most useful for this
purpose. If the vein cannot be distended by proximal compression,
vigourous friction with a piece of dry lint may have the desired
effect--or a test-tube full of water at about 40 deg. C. may be placed
close to the vein. Failing these methods, a drop or two of xylol may be
dropped on the skin just over the vein, left on for a few seconds and
then wiped off with a piece of dry lint.

3. One of the short ends of a 3 by 1 glass slip is brought into contact
with the exuding drop of blood, so that it picks up a small drop.

4. The slide is then lowered transversely on to the surface of a second
3 by 1 slip, which rests on the bench near to one end at an angle of
about 45 deg., and retained in this position for a few seconds, while the
drop of blood spreads along the whole of the line of contact (see also
Fig. 69).

5. Draw the first slide firmly and evenly along the entire length of the
lower slide, leaving a thin regular film which will probably show the
blood cells only one layer thick.