SCOTT, STUDY OF CHANGES IN MUSTELUS CANIS 19 



elasmobranchs and modifications in the molecular concentration of the 

 sea-water. Fresh water has a A of about 0.025°. This is about 1.795° 

 less than that of sea-water. The concentrated solution had an average 

 specific gravity of about l.OSl-f-. The A of such a solution was about 

 2.60°, which is 0.78° greater than that of sea-water. Since the fresh 

 water produced an average rise in the freezing point of the blood of 0.41°, 

 what would be the amount of change in the freezing point of the blood in 

 the concentrated solution if the change in the blood depends upon the 

 change in the molecular concentration of the external medium ? We can 

 formulate the following proportion : 1.795° : 0.41° : : 0.78° : X, where X 

 should equal the change in the blood due to the concentrated solution 

 should the above relation hold true. X equals 0.177° or approximately 

 0.18°; but the observed maximum change in the concentrated solution 

 was 0.24°. There is a difference between the two values of 0.06°. This 

 would indicate that the relation is only roughly if at all proportional. If 

 the changes took place to a different degree or in a different manner in 

 the two solutions, of course any close relationship would be modified. 



Furthermore, do these results show any relation between the degree of 

 change in the freezing point of the blood and the time of immersion ? In 

 the fresh water experiment, eight records were taken between 40 and 45 

 minutes from the beginning. The average time was about 42 minutes. 

 The average time of immersion of all ten fishes was 74 minutes. The 

 average final change in the A of the blood was 0.41°. Therefore in the 

 following proportion, — 74 min. : 42 min. ::0.41° : X, X should have 

 approximately the same value as the A actually observed at the end of 

 the 42 minute period. X equals 0.23°, the theoretical degree of change 

 in A. The observed change in the A of the blood of the eight specimens 

 after 40 to 45 minutes^ immersion in fresh water was 0.18-]-°, showing 

 that the observed change lacked 0.04-|-° of being as great as the calcu- 

 lated change. 



" The average time of immersion in the concentrated solution was 69 

 minutes. Six determinations were made at about 42 minutes from the 

 beginning of the experiment. If the time relation holds in this case, 

 then X in the following proportion should be similar to the observed 

 change in A at the end of the 42-minute period : 69 min. : 42 min. : : 

 0.24° : X. But X equals 0.146°. The observed change in 42 minutes was 

 0.16°. One might conclude from the above considerations that we were 

 dealing here with purely physico-chemical phenomena. It would be haz- 

 ardous, however, to make any sweeping assertions. If we compare the 

 changes in any individual with the average changes in the group, the 

 simple relationships just suggested do not hold. The factors involved 



