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colloids. ia
rounding sea water (A = 2.3°) and varies with the quantity of salt in the
water (Bottazzi). Irf lower fishes (Selachii) the osmotic pressure
of the blood is equal to the surrounding medium, and in higher fishes
(Teleostomi) lower (A = 1.0°) (Bottazzi). In Selachii the osmotic
pressure of the blood is chiefly due to urea (Schroeder). 1
In sea fishes as well as fresh-water fishes, for example, the eel, a lower
osmotic pressure (A = 0.41°) is found when kept in fresh water than
when kept in sea water (A = 0.55°) 2
. In lower sea animals the osmotic
pressure is equal to the surrounding medium, while higher animals are
independent of the surroundings. Hober calls attention to this condi-
tion and points out the analogy with the body heat of the various
animals.3
If we pass to other body fluids we must mention that the lymph
shows a somewhat higher osmotic pressure than the blood, and this is
due to the lymph taking up from the tissues metabolic products hav-
ing a low molecular weight.4
Milk and bile have the same osmotic
pressure as the blood,5
while saliva has a lower pressure.6
The urine
of man and mammalia generally has a much higher osmotic pressure
than the corresponding blood.7
For human urine A varies between 1.3
and 2.3°. After abundant drinking as well as under pathological con-
ditions (diabetes insipidus) the osmotic pressure cf the urine can be lower
than the blood. In regard to the osmetic pressure of animal fluids under
normal and pathological conditions we refer to the work of Koranyi
and Richter. 8
n. COLLOIDS.
The word colloid originated with Graham, who included in this name
different substances which did not have the property of diffusing through
an animal membrane. In opposition to this Graham called those
bodies which passed through a membrane, crystalloids, because they
were as a rule crystalline, a property which with few exceptions does
not belong to the colloids. 9
Graham included soluble silicic acid among
1
Bottazzi, Archives ital. de biol. 28, 61 (1897). Schroeder, Zeitschr. f. physiol.
Chem. 14, 576 (1890).
2
Dekhuisen, Arch, neerland, 10, 121 (1905); Quinton, Compt. rend. boc. biol.,
57, 470, 513 (1904).
3
Physik. Chem. d. Zelle u. Gewebe, 3. Aufl. 353, (1911).
4
Leathes, Journ. of Physiol., 19, 1 (1895).
6
Dresser, Arch. f. exp. Path. u. Pharm., 29, 303 (1892).
.
6
Nolf, Traveaux du lab. de phys. de Liege, 6, 225 (1901).
7
Kordnyi, Zeitschr. f. klin. Med., 33, 1 (1897), 34, 1 (1898).
8
Physikalische Chemie und Medizin. Leipzig (1907).
s
Ann. d. Chem. u. Pharm., 121, 1 (1862) as well as Ann. de chim. et de Phys. (4)„.
3, 127 (1864).
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