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QUANTITY OF BLOOD. 343
produced by a tryptic enzyme which originates from the leucocytes
as well as by traces of a peptic enzyme. A chemical analysis of leucrcmic
blood has been made by Erben.1
A great number of investigations have been made on the chemical
composition of blood in disease. But as we have only a few analyses
of the blood of healthy individuals, and as the possible variations under
physiological conditions are little known, it is difficult to draw any pos-
itive conclusions from the analyses of pathological blood. Unfortunately,
on account of the large number of contradictory deductions concern-
ing the composition of the blood of diseased human beings, it is impossible
to give a brief summary of the results, still the changes in the blood in
disease must be of the greatest importance.
The quantity of blood is indeed somewhat variable in different species
of animals and in different conditions of the b©dy; in general we consider
the entire quantity of blood in adults as about tV-tV (; f the weight of the
body, and in new-born infants about tV- Haldane and Lorrain Smith,2
who have determined the quantity of blood by a new method, find in
fourteen persons that it varies between -fg- and -£$ of the weight of the body.
According to the same method Oerum 3
has determined the quantity
of blood in men as about iV and in woman 2V of the weight of the body.
Fat individuals are relatively poorer in blood than lean ones. During
inanition the quantity of blood decreases less quickly than the weight
of the body (Panum 4
), and it may therefore be also proportionally greater
in starving individuals than in well-fed ones.
By careful bleeding, the quantity of blood may be considerably dimin-
ished without any dangerous symptoms. A loss of blood amounting
to one-fourth of the normal quantity has as a sequence no lasting sink-
ing of the blood-pressure in the arteries, because the smaller arteries
accommodate themselves to the small quantities of blood by contract-
ing (Worm Muller 5
). A loss of blood amounting to one-third of
the quantity reduces the blood-pressure considerably, and a loss of
one-half of the blood in adults is dangerous to life. The more rapid the
bleeding the more dangerous it is. New-born infants are very sensitive
to loss of blood, and likewise fat, old, and weak persons cannot stand
much loss of blood. Women can stand loss of blood better than men.
The quantity of blood may be considerably increased by the injection
of blood from the same species of animal (Panum, Landois, Worm
1
Zeitschr. f. klin. Med., 66 (1908).
2
Journ. of Physiol., 25.
3
Deutsch. Arch. f. klin. Med., 93 (1908).
4
Yirchow’s Arch., 29.
5
Transfusion und Plethora, Christiania, 1875.
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