KONINKLIJKE AKADEMIE VAN WETENSCHAPPEN 
TE AMSTERDAM, 
PROCEEDINGS OF THE MEETING 
of Saturday February 25, 1905. 
IEC 
(Translated from: Verslag van de gewone vergadering der Wis- en Natuurkundige 
Afdeeling van Zaterdag 25 Februari 1905, DI. XIII). 
CGliOEN FERNS: 
M. C. Dexuuyzen: “On the osmotic pressure of the blood and urine of fishes”. (Communicated 
by Prof. C. A. PEKELHARING), p. 537. 
H. ZWAARDEMAKER Cz.: “On the relative sensitiveness of the human ear for tones of different 
pitch, measured by means of organ pipes”, p. 549. 
H. W. Baxuuis Roozesoom and E. H. Bucuner: “Critical terminating points in three-phase 
lines with solid phases in binary systems which present two liquid layers”, p. 556. 
P. H. Scnoure: “On non-linear systems of spherical spaces touching one another”, p. 562. 
JAN DE Vries: “On a special tetraedal complex”, p. 572. 
Jan DE Vries: “On a group of complexes with rational cones of the complex”, p. 577. 
M. W. Berserinck: “An obligative anaerobic fermentation sarcina”, p. 580. 
H. A. Lorentz: “The motion of electrons in metallic bodies”, II., p. 588. 
The following papers were read: 
Physiology. — “On the osmotic pressure of the blood and urine of 
fishes” By Dr. M. C. Deknuyzer at Utrecht. (Communicated 
by Prof. C. A. PEKELHARING.) 
(Communicated in the meeting of November 26, 1904). 
Migratory fishes (eel, salmon, shad) move in a relatively short 
time from sea-water, having an osmotie pressure of about 24 atmo- 
spheres, into fresh water, in which this pressure is */, of an atmo- 
sphere or less, without experiencing any harm. And this same transition 
also takes place in the opposite direction. It is very mysterious how 
such an emancipation from the laws of osmotic pressure is possible. 
It is known in general outlines that bony fishes, as well in salt as 
in fresh water, keep up an osmotic pressure in their blood which is 
relatively independent of that of the surrounding medium. But it is 
37 
Proceedings Royal Acad. Amsterdam. Vol. VIL. 
