SCOTT, STUDY OF CHANGES IN MUSTELUS CANIS 9 



were placed in a large tank of sea-water. The salt water supply was then 

 shut off and a stream of fresh water was turned into the tank. In a few 

 minutes the water in the tank was fresh. After certain periods of im- 

 mersion, the specimens were removed and a small quantity of blood was 

 drawn from the caudal artery of each for a freezing point determination. 

 It will be noted in the experiments that follow that the normal A of the 

 blood of each animal is not given. But one freezing point determination 

 was made in each case and that at the end of the time of immersion in 

 the experimental medium. It should be borne in mind, however, that the 

 mean A of the normal blood of Mustelus is about 1.87°. The results of 

 the first experiment are as follows : 



Table II. 



-Change in the freezing point of the Mood after various periods of 

 immersion in fresh water 



(A of fresh water = 0.025 °) 



Specimen 



Immersion time in 

 minutes 



A of blood 



1 

 2 

 3 

 4 

 5 

 6 



35 

 40 

 60 

 60 

 75 

 90 



1.62 ° 



1.565 



1.585 



1.610 



1.495 



1.54 



Individual changes in the freezing point of the blood are not the same 

 for the same time of immersion. In a general way, however, the osmotic 

 pressure becomes progressively less as the time of immersion increases. 



I next concluded to ascertain the relation of change in the freezing 

 point of the blood to solutions less dilute than fresh water. In the second 

 experiment a solution of one-half sea-water and one-half fresh water was 

 employed. The A of this solution is about 0.90°. The results are as fol- 

 lows: 



Table III. — Showing the change in the freezing point of the Mood after various 

 periods of immersion in one-half sea-ivater and one-half fresh water 



Specimen 



Immersion time in 

 minutes 



A of blood 



1 



2 

 3 

 4 

 5 



50 



75 



100 



200 



245 



1.77 ° 



1.705 

 1.685 

 1.595 

 1.555 



