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QUANTITATIVE COMPOSITION OF THE BLOOD. 327
of a fluid which prevents coagulation. This mixture is introduced into
a tube and then centrifuged. According to Hedin it is best to treat the
blood, which is kept fluid by 1 p. m. oxalate, with an equal volume of
a 9 p. m. NaCl solution. After complete centrifugalization, the layer of
blood-corpuscles is read off on the graduated tube and the volume of
blood-corpuscles (or more correctly the layer of blood-corpuscles) in 100
vols, of the blood calculated therefrom. By means of comparative counts,
Hedin and Daland have found that an approximately constant relation
exists between the volume of the layer of blood-corpuscles and the number
of red corpuscles under physiological conditions, so that the number of
corpuscles may be calculated from the volume. Daland x
has shown
that such a calculation gives approximate results also in disease, when
the size of the blood-corpuscles does not essentially deviate from the
normal. In certain diseases, such as pernicious anaemia, this method
gives such inaccurate results that it cannot be used.
Koppe 2
has showTi that in centrifuging blood very rapidly, more
than 5000 turnes per minute, the blood-corpuscles may be so completely
separated that all intermediate fluid is removed. Because of the absence
of this intermediate fluid the refraction is changed; the outer layers of
the erythrocytes containing fat become transparent, and the column
of blood-corpuscles becomes transparent and laky. If the volume of
the separated column of blood-corpuscles is determined and the number
of red blood-corpuscles counted, the absolute volume of these latter
can be determined by this method.
In determining the relation between the weight of blood-corpuscles and
the weight of blood-fluid, we generally proceed in the following manner:
If any substance is found in the blood which belongs exclusively to
the plasma and does not occur in the blood-corpuscles, then the amount of
plasma contained in the blood may be calculated if we determine the
amount of this substance in 100 parts of the plasma or serum respectively
on the one side, and in 100 parts of the blood on the other. If we repre-
sent the amount of this substance in the plasma by p and that in the
blood by b, then the amount of x in the plasma from 100 parts of blood is
100.6
x = .
P
Such a substance, which occurs only in the plasma, is fibrin according
to Hoppe-Seyler, sodium according to Bunge (in certain kinds of blood).
The experimenters just named have tried to determine the amount of the
plasma and blood-corpuscles, respectively, in different kinds of blood,
starting from the above-mentioned substances.
Another method suggested by Hoppe-Seyler is to determine the
total amount of haemoglobin and proteins in a portion of blood, and on
the other hand the amount of haemoglobin and proteins in the blood-
corpuscles (from an equal portion of the same blood) which have been
sufficiently washed with common-salt solution by centrifugal force. The
figure obtained, as a difference between these two determinations, corre-
sponds to the amount of proteins which was contained in the serum of
1
Hedin, Skand. Arch. f. Physiol., 2, 134 and 361, and 5; Pflliger’s Arch., t>0;
Daland, Fortschritte, d. Med., 9.
2
Pfluger’s Arch., 107.
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