vessels: which are then weighed,
dried at 65 deg.-70 deg. C. for 24 hours and then weighed again. The figures so
obtained for the dried substance have a certain independent importance;
for they do not run quite parallel with those of the specific gravity,
amount of haemoglobin or number of corpuscles. The normal values are, for
men 21.26%, for women 19.8%.

A further procedure for obtaining indirect evidence of the amount of
haemoglobin is the DETERMINATION OF THE VOLUME OF BLOOD CORPUSCLES IN 100
PARTS OF TOTAL BLOOD. For this estimation a method is desirable, which
allows of the separation of the corpuscles from plasma in blood, that is
as far as possible unaltered. The older methods do not fulfil this
requirement; since they recommend either defibrination of the blood
(quite impossible with the quantities of blood which are generally
clinically available); or keeping it fluid by the addition of sodium
oxalate or other substances which prevent coagulation. The separation of
the two constituents can be effected by simply allowing the blood to
settle, or with the centrifugal machine, specially constructed for the
blood by Blix-Hedin and Gaertner ("Haematocrit").

For these methods various diluting fluids are used, such as
physiological saline solution, 2.5% of potassium bichromate and many
others. According to H. Koeppe they are not indifferent as far as the
volume of the red blood corpuscles is concerned; and a solution which
does not affect the cells must be previously ascertained for each
specimen of blood. For this reason attention may be called to the
proceeding of M. Herz, in which the clotting of the blood in the pipette
is prevented by rendering the walls absolutely smooth by the application
of cod-liver oil. Koeppe has slightly varied this method; he fills his
handily constructed pipette, very carefully cleaned, with cedar wood
oil, and sucks up the blood, as it comes from the fingerprick into the
filled pipette. The blood displaces the oil, and as it only comes into
contact with perfectly smooth surfaces, it remains fluid. By means of a
centrifugal machine, of which he has constructed a very convenient
variation, the oil as the lighter body is completely removed from the
blood; and the plasma is also separated from the corpuscles. Three
sharply defined layers are then visible, the layer of oil above, the
plasma layer, and the layer of the red blood corpuscles. In as much as
the apparatus is calibrated, the r