SCOTT, STUDY OF CHANGES IN MUSTELUS CANI8 15 



more rapid changes in the osmotic pressure of the blood. Toward the 

 end of the time, less rapid changes are again indicated. The ordinate 

 which determines the last part of the curve is the average of but two 

 determinations, because most of the animals died before the immersion of 

 a hundred minutes. The ordinate at D more correctly represents the aver- 

 age condition at death. That part of the curve from jST to D represents 

 graphically the course of the change in the freezing point of the blood 

 from the normal condition until near death in fresh water. It may be 

 thought that the initial slowness of the changes in the osmotic pressure 

 of the blood is due to the fact that the water is changing from salt to 

 fresh during this period. The slowness, however, continues longer than 

 the time required for the 

 change from salt to fresh *o.a(p 

 water. The period of ac- 

 celeration may be due to 

 the gradual failure of the -^o^o" 

 defences of the organ- 

 ism. It is possible that 



the first part of the curve ^"j^ ^u ^. ^o- so- loo' 



represents changes due a b c d e 



merely to the entrance of ^'^- i--^'*"^^^ "^ A of uood of Musteius due to 



^ ^ immersion m fresh water until death 



water into the blood of 



the animal. From this point of view, the second part of the curve might 

 indicate the passage of dissolved substances such as salts out from the 

 blood through the limiting membranes of the body into the water out- 

 side while the outside water continued to pass into the blood. This would 

 mean, of course, profound changes in the physico-chemical constitution 

 of the organism. Dakin ('08) found that the maximum change in the 

 freezing point of the blood of three specimens of Acanthias vulgaris after 

 immersion in fresh water until near death was 0.465°. Garrey found 

 the maximum change in the freezing point of the blood of one Musteius 

 to be 0.37°. My observations range from 0.27° to 0.50°. That the mag- 

 nitude of the change is not due to the amount of blood taken is shown 

 from the records of specimens 1 and 2. The maximum change in case 

 of No. 1 is .33°, while that of No. 2 was .43°, though six samples of 

 blood were taken from the first specimen, while but four samples were 

 taken from the second specimen. Other cases of the kind can be found. 



EFFECT OF A CONCENTRATED SOLUTION OF SEA-WATER 



The change in the osmotic pressure of the blood from the normal con- 

 dition until death in a concentrated solution of sea-water was next ob- 



