ons this method is far too clumsy for practical
purposes.

Quincke has endeavoured to calculate the amount of blood in cases of
blood transfusion for therapeutic purposes. From the number of red blood
corpuscles of the patient before and after blood transfusion, the amount
of blood transfused and the number of corpuscles it contains, by a
simple mathematical formula the quantity of the blood of the patient can
be estimated. But this method is only practicable in special cases and
is open to several theoretical errors. First, it depends upon the
relative number of red blood corpuscles in the blood; inasmuch as the
transfusion of normal blood into normal blood, for example, would
produce no alteration in the count. This consideration is enough to shew
that this proceeding can only be used in special cases. It has indeed
been found that an increase of the red corpuscles per cubic millimetre
occurs in persons with a very small number of red corpuscles, who have
been injected with normal blood. But it is very hazardous to try to
estimate therefrom the volume of the pre-existing blood, since the act
of transfusion undoubtedly is immediately followed by compensatory
currents and alterations in the distribution of the blood.

No property of the blood has been so exactly and frequently tested as
the NUMBER OF RED CORPUSCLES PER CUBIC MILLIMETRE OF BLOOD. The
convenience of the counting apparatus, and the apparently absolute
measure of the result have ensured for the methods of enumeration an
early clinical application.

At the present time the instruments of Thoma-Zeiss or others similarly
constructed are generally used; and we may assume that the principle on
which they depend and the methods of their use are known. A number of
fluids are used to dilute the blood, which on the whole fulfil the
requirements of preserving the form and colour of the red corpuscles, of
preventing their fusing together, and of allowing them to settle
rapidly. Of the better known solutions we will here mention =Pacini's= and
=Hayem's= fluids.

Pacini's solution. Hydrarg. bichlor. 2.0
Natr. chlor. 4.0
Glycerin 26.0
Aquae destillat. 226.0

Hayem's solution. Hydrarg. bichlor. 0.5
Natr. sulph. 5.0
Natr. chlor. 1.0
Aquae destillat. 200.0