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BLOOD SERUM. 271
A Macallum l
has determined the quantity of mineral bodies in
the serum of certain , cold-blooded animals (fishes, shark, lobster and
others). The amount of sodium and chlorine in the serum of these animals
living in sea-water was much greater than in warm-blooded animals.
Even if we bear in mind that certain bodies, such as carbon dioxide,
arc driven oft" during incineration, and that other bodies, such as sul-
phuric acid and phosphoric acid, are formed from sulphurized and
phosphorized organic substances, still quantitative analyses like the
above are not sufficient for the scientific demands of to-day. They
do not show the true composition, and especially do not give an explana-
tion of the number of different ions present in the serum or in other fluids,
a question which is of the greatest physiological importance. An
answer to these questions is obtainable only by physico-chemical investiga-
tions, which have thus far been used chiefly in determining the molecular
concentration, the amount of electrolytes and non-electrolytes, and the
degree of dissociation.
The average depression of the freezing-point of mammalian blood
corresponds, as given in Chapter I, closely to a 9 p. m. (A = about
—0.56°) solution of common salt, and at the present time such a solution
is considered as a physiological salt solution for man and other mammalia.
In lower animals and fish the conditions are otherwise, as shown in
the above-mentioned chapter.
There are recorded a great number of investigations on the changes
in the osmotic pressure or the molecular concentration of the blood-
serum under various physiological conditions as wr
ell as in disease, but
still it is no doubt too early to draw any definite conclusions from these
observations.
The degree of dissociation (see Chapter I) of sera has been determined
by several investigators, and according to Hamburger 2
it lies between
0.65 and 0.82. The molecular concentration, which represents the
total number of molecules and ions per liter, is according to Bvrgarsky
and Tangl, on an average about 0.320 mol. per liter. They also
found that about three-fourths of the total number of dissolved mole-
cules in blood-serum were electrolytes, although the serum contained
about 70-80 p. m. protein and 10 p. m. inorganic bodies, and also that
three-fourths of the quantity of electrolytes consisted of NaCl.
In the determination of the alkalinity of blood and blood-serum,
up to the present time, we have estimated the amount of alkali by titra-
tion with an acid. We cannot dispense v ith such d< terminations, although
iProc. Roy. Soc, ser. B., 82.
2
Osmotisher Druck und Ionenlehre, Wiesbaden, 1902-1904, where the literature
on the physical chemistry of the blood can be found.
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