532 
BULLETIN OF THE BUREAU OF FISHERIES 
MAGNESIUM SALTS 
The r61e of magnesium salts in the blood of animals is not so well understood as 
that of some of the other salts, but as magnesium compounds occur in the blood of 
fresh-water mussels and also in the water (often in relatively large amounts), in 
which these animals live, a series of mussels were tested in solutions of magnesium 
salts. The data for these series are given in Table 15 and Figure 12. 
As far as determined by these series, the adjustment to magnesium salts, if they 
be present in amounts which can be tolerated, is made rather quickly. Mussels 
Figure 12.— Specific gravity of the blood of fresh-water mussels in tap 
water plus magnesium salts. All animals with valves propped open. 
Black circle, 1 per cent magnesium sulphate; circle 0.5 per cent 
magnesium sulphate; black triangle, 0.25 per cent magnesium sul- 
phate; and square 0.5 per cent magnesium chloride 
transferred to 1.00 per cent solution of magnesium sulphate showed the same rather 
abrupt rise in specific gravity of the blood during the first 24 hours as that noted for 
the salts of sodium and potassium, and 0.50 per cent solutions of magnesium sulphate 
and magnesium chloride produced lesser elevations of the blood specific gravity. 
Beyond the first 24 hours, the results suggest a return to normal blood specific gravity 
or below, although the data are scant. From the reactions of the mussels to the vari- 
ous solutions of magnesium salts used, the toxicity of magnesium compounds seems 
much less than that of either potassium or sodium salts, but it must be remembered 
in this connection that the permeability of living cells to magnesium salts is quite 
different from that to either potassium or sodium salts. 
