(539 ) 
is considerably diluted by the rains. There are reasons for assuming 
that these influences make themselves felt in the osmotic pressure of 
the blood. An investigator who should stay for a long time at Ber- 
gen, choose his material carefully, keep it for some time in aquaria 
and note for each specimen everything that could have any influence, 
would without doubt obtain more constant results than can be published 
here. Still it would be more recommendable to accompany the fisher- 
men and to collect blood and urine immediately after the catching. 
The figures here given must be judged as one of the first attempts 
in this almost unexplored region. Only during and by my investigation 
I have become aware of the necessity of taking the condition of 
health of the animals very much into account. 
The specimens bought were conveyed to the biological station 
either in pails of seawater or without this precaution, a distance of 
twenty minutes. and placed there again in aquaria in which sea- 
water circulated containing about 32°,°, salt, corresponding to a 
freezing point of —1.731° to —1.742°. The fishes that showed 
signs of debility were examined first, the others remained for some 
hours and even for two or three days in a spacious aquarium 
without special food. Many specimens proved to have still filled 
stomachs and to lodge few parasites, others were in a less satis- 
factory condition, but all these details were not recorded. The 
quantity of blood furnished by each fish is relatively small and 
varies as well with different species as with different individuals. 
As a rule, for a determination of the freezing point the blood of 
several specimens is required, since ten to fourteen cubic centimetres 
must be put into the freezing tube. The fishes were washed in 
tapwater, well wiped and their tails cut off with a pair of bone- 
scissors. Sometimes it appeared to be necessary to make an incision 
in the heart; in this case the gills were once more cleaned from 
seawater with a dry towel. 
Would it not be better to use serum? This does not appear to 
be necessary to me, since the same sample of blood generally gives 
the same freezing point in repeated measurements and later a serum | 
separates which as a rule is not coloured red, even with Raja clavata 
and Trygon pastinaca which are supercooled to — 2.7°. Also Hrpin 
and Hampurcrr’) have found that it is not necessary to separate 
the serum. ; 
In order to diminish the quantity of blood necessary for a deter- 
mination, which is desirable especially with small or rare species, I 
1) Hampurcer, Osmotischer Druck und Ionenlehre in den medicinischen Wis- 
senschaften. Wiesbaden 1902. IL. p. 453. 
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