536 
BULLETIN OF THE BUREAU OF FISHERIES 
Blood samples were taken at intervals and only those mussels which were closed 
at the time the sample was to be taken were used. The determinations of specific 
gravity for the blood from the 28 individuals which survived this treatment are given 
in Table 17 and Figure 14. 
During the first four hours of exposure to air the rise in blood specific gravity be- 
came evident. This may have resulted from either the loss of water from the blood, 
or from the addition of calcium salts to the blood to buffer down the products of 
Figure 14. — Blood specific gravity of mussels exposed to air. Upper half, in air at room tem- 
perature; lower half, in air on ice 
respiration in the animal now deprived of its regular supply of fresh water; or both 
factors may have contributed to the rise in specific gravity. 
The specific gravity of the blood continued to rise throughout the test. It was 
noted that those mussels which remained closed survived, while those which opened 
the valves and thereby lost some or all of the water which had been retained between 
the valves when the animal closed, as it was being taken from the river, soon suc- 
cumbed. 
The pH value of the blood remained near pH 7.7 in most of the animals from 
which samples were taken, but all moribund animals were rejected in this series. 
