The spleen and lymphatic glands were at first regarded as the sole
places of formation of the blood corpuscles. The almost simultaneous
researches of Neumann and Bizzozero first attracted general attention to
the importance of the bone-marrow. These authors showed that the early
stages of the red blood corpuscles are produced there; a discovery which
was quickly and generally recognised, and which soon became
pathologically useful through the observations of Cohnheim and others.
In this connection the observation was of great value, that after severe
loss of blood the fatty marrow of the larger hollow bones again changes
to red marrow, as it is evidence of the increased demands on the
regenerative function of the bone-marrow.

We are unaware of a second place of formation of the red blood
corpuscles in man. In other mammalia however, as we have above mentioned
(see page 99), the spleen may also take a small share in the production
of erythrocytes. The type which the normal blood formation follows in
adults, and the deviations therefrom shewn in pernicious anaemia, have
been described in the chapter on the red blood corpuscles. Ehrlich's
view that the blood formation in pernicious anaemia belongs to a
different type, which is analogous to the embyronic, was also described
there.

In this section we have therefore to deal chiefly with the white blood
corpuscles and their connection with the bone-marrow. In man as in a
large number of animals (for example the monkey, guinea-pig, rabbit,
pigeon and so forth) =the bone-marrow exhibits the peculiarity that the
cells it produces bear a specific granulation, in sharp contrast to the
lymphatic glandular system, which contains elements free from granules,
in the whole animal series=.

The granulated cells of the bone-marrow fall into two groups.

The first group of the cells with "=special granules=" is very important
since it constitutes a characteristic for certain species of animals.
According to the class of animal they shew different tinctorial and
morphological properties. Man and monkey for example have neutrophil
granulation; guinea-pig and rabbit the pseudo-eosinophil granulation
described by Kurloff; in birds we find two specific granulations present
side by side, which both are oxyphil, and of which one is imbedded in
the protoplasm in crystalline form, the other in the form of granules.

The kinds of special granulations so far investigated have the common
pro