22 



ANNALS NEW YORK ACADEMY OF SCIENCES 



blood was drawn after they had been immersed for about an hour. The 

 results were as follows : 



Table VI. — Showing the depression of the freezing point of the serum of 

 Mustelus in salt tcater and after immersion in fresh icatcr for one hour 



Serum from normal fishes 



Serum from fishes immersed 

 in fresh water one hour 



No. specimen 



A 



No. specimen 



A 



1 

 1 

 2 

 2 

 1 



1.920° 



1.950 



1.805 



1.950 



1.947 



1 

 4 

 2 

 2 

 2 



1.580° 



1.460 



1.595 



1.595 



1.540 



Average, 1.914° 



Average, 1.554° 



The average rise in the freezing point of the serum of these dog-fish 

 after immersion in fresh water for an hour is thus seen to be +0.36°. 



CHANGES IX THE OSMOTIC PEESSUEE OF THE BLOOD BBOUGHT ABOUT BY A 

 EETUEN TO SEA-WATEE AFTEE IMMEESION IN FEESH WATEE OE CONCEN- 

 TEATED SEA-WATEE 



The above experiments on the effects of diluted and concentrated solu- 

 tions of sea-water indicate that to cause a decrease in osmotic pressure 

 with the diluted solutions there must be currents outward through the 

 limiting membranes of the body ; to cause an increase with concentrated 

 solutions there must be currents inward. I^ it possible to demonstrate 

 these two effects in the same individual ? If reversibility is possible, then 

 after a fall in osmotic pressure resulting from immersion in a diluted 

 solution of sea-water, the original pressure should apparently be gained 

 when the animal is returned to normal sea-water. The experiments re- 

 ported in Table IX were carried out to test this possibility. 



Table IX. — Effect on the hlood of transference of Mustelns from sea-icater to 

 fresh ivater folloiced J)y subsequent return to sea-water 



Sea-water 



Fresh water 



Sea-water 



Normal A 



of blood 



in degrees 



Duration of 

 immersion 

 in minutes 



A of 

 blood 



Change 



from 

 normal 



Duration of 

 immersion 

 in minutes 



A of 

 blood 



Change 



from 

 normal 



Amount 



of 

 reversal 



1=1.835 

 2=1.895 

 3=1.875 

 4=1.905 



35 



55 

 30 

 25 



1.620° 

 1.655 

 1.675 

 1.665 



+0.215° 

 +0.240 

 +0.200 

 +0.240 



25 



50 



50 



100 



1.685° 



1.785 



1.760 



1 . 785 



+0.15 ° 

 +0.115 

 +0.115 

 +0.120 



0.065° 

 0.125 

 0.085 

 0.120 



