eater number
of cases, if not in all, Oligaemia and Oligocythaemia to a greater or less
extent occur simultaneously.

The most important methods of clinical haematology bear directly or
indirectly on the recognition of these conditions.

There is at present no method of ESTIMATION OF THE TOTAL QUANTITY OF THE
BLOOD which can be used clinically. We rely to a certain extent on the
observation of the already mentioned symptoms of redness or pallor of
the skin and mucous membranes. To a large degree these depend upon the
composition of the blood, and not upon the fulness of the peripheral
vessels. If we take the latter as a measure of the total amount of
blood, isolated vessels, visible to the naked eye, _e.g._ those of the
sclerotic, may be observed. Most suitable is the ophthalmoscopic
examination of the width of the vessels at the back of the eye. Raehlmann
has shewn that in 60% of the cases of chronic anaemia, in which the skin
and mucous membranes are very white, there is hyperaemia of the
retina--which is evidence that in such cases the circulating blood is
pale in colour, but certainly not less in quantity than normally. The
condition of the pulse is an important indication of diminution of the
quantity of the blood, though only when it is marked. It presents a
peculiar smallness and feebleness in all cases of severe oligaemia.

The bleeding from fresh skin punctures gives a further criterion of the
quantity of blood, within certain limits, but is modified by changes in
the coagulability of the blood. Anyone who has made frequent blood
examinations will have observed that in this respect extraordinary
variations occur. In some cases scarcely a drop of blood can be
obtained, while in others the blood flows freely. One will not err in
assuming in the former case a diminution of the quantity of the blood.

The fulness of the peripheral vessels however is a sign of only relative
value, for the amount of blood in the internal organs may be very
different. The problem, how to estimate exactly, if possible
mathematically, the quantity of blood in the body has always been
recognised as important, and its solution would constitute a real
advance. The methods which have so far been proposed for clinical
purposes originate from Tarchanoff. He suggested that one may estimate
the quantity of blood by comparing the numbers of the red blood
corpuscles before and after copious sweating. Apart from various
theoretical considerati