24: ANNALS NEW YORK ACADEMY OE SCIENCES 



described. In the first, three dog-fishes were used. The A of the com- 

 bined blood of the three was 1.92°. They were then placed in a concen- 

 trated solution of sea-water having a A of about 2.60° for forty minutes, 

 at the end of which time the A of the mixed blood from the three was 

 2.11°, the freezing point having fallen 0.19°. Then the specimens were 

 returned to sea-water for eighty minutes, when A was 2.04°, showing that 

 although the freezing point had risen 0.07°, it still lacked 0.12° of being 

 normal. In the second experiment, three dog-fishes were also used. The 

 normal A of their mixed blood was 1.87°. They were placed for sixty 

 minutes in a tank containing a concentrated solution of sea-water having 

 a A of about 2.15°. At the end of this time the A of their mixed blood 

 was 2.00°, showing a fall in the freezing point of 0.13°. The three speci- 

 mens were then returned to a concentrated solution having a A of 2.60° 

 for sixty minutes more, at the end of which time the A of their combined 

 blood was 2.18°, showing a total fall in the freezing point of the blood of 

 0.31°. Sea-water was then run into the tank for two and one-half hours 

 when the value of the A of the blood was 1.98° ; that is in the two hours 

 and a half after the return to sea-water the freezing point of the blood 

 rose 0.20°, but was still 0.11° short of its value at the beginning of the 

 experiment. Thus with neither a hypotonic nor a hvpertonic medium did 

 the organisms regain the normal A after the return to sea-water even 

 though they were kept in the sea-water as long or even longer than in the 

 diluted or concentrated solution. 



One other experiment of this nature will be referred to briefly A 

 somewhat small stream of concentrated sea-water was passed into the 

 mouth and out through the gills of a l^rge female dog-fish for 45 min- 

 utes. The A of its blood fell 0.09°. The small size of the stream possibly 

 explains the small change in A. A stream of fresh water was then turned 

 on gradually and A was again taken 60 minutes later. A proved to be 

 h n n.^oT V ''" *^' concentrated solution and was even higher 

 by 0.07 than the normal. The fish was then returned to sea-water for 

 60 minutes when A was 0.03° lower than the normal. In this case we 

 have evidence of an increase in the osmotic pressure of the blood due to a 

 conceii rated external medium. A fall in the osmotic pressure results 

 V. hen the organism is subjected to a dilute external medium, after which 

 It rises to the normal condition when the animal is returned to sea-water. 

 It should be noted that, in changing the concentrated solution to fresh 



TaV^lT'Tlf "'"*"" "^^ ^^^^^^"^ -Pl-^^ by fresh water 

 befn! 1 20 " 1 ' 1" T"'*'' ''''''' ^^^ ^'^b -- --^«-lIy large, 

 out of the water and the stream entered its mouth through a rubber tube 



