( 549 ) 
With a large specimen of the sea-wolf, whose blood had given A 
0.681°, the urine gave 0.631°. With other individuals I found 0.555°. 
The urine taken from some twenty specimens of G. virens gave 
4 0.630°. With the cod 0.652 and 0.619 have been stated. 
It is very simple to take the urine. A sea-wolf, e.g. is taken 
behind the gills and suddenly lifted from the seawater, the skin of 
the belly is dried, while the assistant stands ready for collecting the 
urine which often is ejected in a vigorous jet. By some pressure 
on the belly a little more is obtained, but often the “bladder” (the 
extended part of the ureters) is empty. Most animals gave little or 
nothing and were given back to the seller so that a comparison of 
4 of the hlood and urine was only possible in exceptional cases. 
At Bergen I had for the three species that were studied, found not 
a single figure for 4 that was lower for the blood than for the 
urine. At Amsterdam, however, it has appeared that there also 
occur specimens, the blood of which shows a still somewhat smaller 
osmotic pressure than any of the urines (cod). 
The remarkably low /P, of the secreted product of the kidneys 
with marine Teleosteans certainly points to this: that these animals 
do not keep the osmotic pressure in their blood 23—8.6=—14.4 atmo- 
spheres lower because the kidneys so quickly eliminate the surplus 
of salts taken in. The relative richness in water of the urine rather 
points to these fishes resorbing from the sea-water in opposition to the 
osmotic pressure, hence by using chemical energy, water or if one 
prefers, a diluted solution of salt. But Rrexarp has stated (l.c. p. 391) 
that certain freshwater fishes secrete from their gills soluble car- 
bonates! About the mechanism of ideotony we are still in the dark. 
Physiology. — “On the relative sensitiveness of the human ear for 
tones of different pitch, measured by means of organ pipes.” 
By Prof. H. ZWAARDEMAKER Cz. 
(Communicated in the meeting of January 28, 1905.) 
Almost simultaneously, but by different methods, the relative 
sensitiveness of the human ear as depending on pitch, was investigated 
by Max Wier!) and by F. H. Quix and myself’). The result of 
1) Max Wren. Physik. Ztschr. IV p. 69. Pfliiger’s Archiv Bd. 97. p. 1. 1903. 
2) ZWAARDEMAKER and Qurx. Ned. Tijdschr. v. Geneesk. 1901 II p. 1374: 1902 
Il p. 417. and Engelmann’s Archiv. 1902 suppl. p. 367. 
