ion.

II. ON THE PLACES OF ORIGIN OF THE WHITE BLOOD CORPUSCLES.

For the comprehension of the histology of the blood as a whole, it is of
great importance to obtain an exact knowledge how and to what extent the
three organs, which are undoubtedly very closely connected with the
blood, lymphatic glands, bone-marrow, and spleen, contribute to its
formation. The most direct way of deciding the question experimentally
by excision of the organs in question, is unfortunately only available
for the spleen. The part played by the lymphatic glands and bone-marrow,
whose exclusion _in toto_ is not possible, must mainly be determined by
anatomical and clinical considerations. But only by a careful
combination of experiments on animals, of anatomical investigations, and
especially, of clinical observations on a large scale, can light be
thrown on these very difficult questions. It cannot be emphasised
sufficiently how important it is that everyone engaging in haematological
work should first of all collect a large series of general observations;
otherwise errors are bound to occur. For instance, the endeavour is
often made to compensate the lack of personal experience by careful
literary studies; but in this way the histology of the blood falls into
a vicious circle, of which the new phase of blood histology affords
many examples. And it is characteristic of this kind of work that from
the investigation of a single rare case, most far-reaching conclusions
on the general pathology of the blood are at once drawn; _e.g._ Troje's
paper, in which having failed to recognise the lymphocytic character of
a case of leukaemia, and believing therefore that he had to do with a
myelogenous leukaemia, the author denied and completely reversed all that
had been previously established about this disease. It is equally hard
to avoid errors if one confines oneself exclusively to animal
experiments, without supplementing these by clinical experience, as is
shewn by the numerous papers of Uskoff. Not the anatomist, not the
physiologist, but only the clinician is in the position to discuss these
problems.

In the introduction to this chapter we have already alluded to the
striking retrograde movement in haematology at the present time, brought
about by the view that the white corpuscles as a whole are derived from
the lymphocytes. If we disregard the embryological investigations on
this point (Saxer), anatomists, physiologists, and clinician