btained
was 0.89%. Only in a few cases of skin disease was a slight increase
indicated. The average amounted to 0.58%, a number, therefore, which is
often to be found in healthy individuals. A leucocytosis of mast cells,
comparable with the eosinophil or neutrophil forms of leucocytosis, has
not been demonstrated in the cases of Canon or other observers. On the
other hand, the mast cells undergo a considerable increase in myelogenic
leukaemia, in many cases equalling or even exceeding that of the
eosinophils. We shall not err in deriving the mast cells of the blood
solely from the bone-marrow, on the grounds of this fact; or in
conjecturing that their origin is not from the connective tissue, even
when they are there excessively increased[30].

We think we have shewn in the preceding paragraphs that the evidence, so
far brought forward for a local origin of the eosinophil cells, does not
withstand the objections that have been raised. The task now lies before
us, to produce positive proof that the accumulations of eosinophil cells
in the organs and secretions must be explained by emigration from the
blood.

This proof offers great difficulties in as much as we normally find
eosinophil cells in many places. Here then we cannot trace a process
step by step, but we have to deal with final conditions. Could we
observe the genesis of eosinophil cells in organs usually free from
them, it would be easier to clear up this question. Up to the present
but a single observation on this point is available. Michaelis
established the interesting fact, that on interrupting lactation in
suckling guinea-pigs, in the course of a few days numerous eosinophil
cells collect in the mammary glands, but not in the lumen of the
canaliculi. The eosinophil cells are further polynuclear, exactly
corresponding to those of the blood, and therefore to be regarded as
immigrants. We may explain this condition according to modern views as
follows. Under certain conditions the mammary gland is capable of an
internal secretion, by means of which substances are produced that are
specifically chemiotactic for the eosinophil cells. When the external
secretion of milk is disturbed, the internal secretion is abnormally
increased. The fact too that in Michaelis' researches no eosinophil cells
passed into the true secretion of the gland may be thus explained[31].

Exactly similar observations have been made on pathological material,
first recorded in the brill