since the
histological appearance of the blood gives it no support. Koeppe, who
has specially directed part of his researches to the morphological
phenomena produced during acclimatisation to high altitudes, has shewn,
that in the increase of the number of red corpuscles two mutually
independent and distinct processes are to be distinguished. He observed
that, although the number of red corpuscles was raised so soon as a few
hours after arrival at Reiboldsgruen, numerous poikilocytes and
microcytes make their appearance at the same time. The initial increase
is therefore to be explained by budding and division of the red
corpuscles already present in the circulating blood. Koeppe sees in
this process, borrowing Ehrlich's conception of poikilocytosis, a
physiological adaptation to the lower atmospheric pressure, and the
resulting greater difficulty of oxygen absorption. The impediment to the
function of the haemoglobin is to a certain extent compensated, since the
stock of haemoglobin possesses a larger surface, and so is capable of
increased respiration. So also the remarkable fact may be readily
understood that the sudden rise of the number of corpuscles is not at
first accompanied by a rise of the quantity of haemoglobin, or of the
total volume of the red blood corpuscles. These values are first
increased when the second process, an increased fresh production of
normal red discs, takes place, which naturally requires for its
developement a longer time. The poikilocytes and microcytes then vanish,
according to the extent of the reproduction; and finally a blood is
formed, which is characterised by an increased number of red corpuscles,
and a corresponding rise in the quantity of haemoglobin, and in the
percentage volume of the corpuscles.

Other authors infer a relative and not an absolute increase in the
number of red corpuscles. E. Grawitz, for example, has expressed the
opinion that the raised count of corpuscles may be explained chiefly by
increased concentration of the blood, due to the greater loss of water
from the body at these altitudes. The blood of laboratory animals which
Grawitz allowed to live in correspondingly rarefied air underwent
similar changes. Von Limbeck, as well as Schumburg and Zuntz, object to
this explanation on the ground, that if loss of water caused such
considerable elevations in the number, we should observe a corresponding
diminution in the body weight, which is by no means the case.