BLOOD OF FRESH-WATER MUSSELS 
525 
siphons are protruded cautiously so that little of the water in the new location is 
taken inside of the shell for some time. In order, therefore, that the test solution 
might have access to the soft parts of the animal at once, the mussels were allowed 
to close on small bits of cork (as described in the section on foot strips) before the 
transfer to the test solution. Unless otherwise specified, the valves of all mussels 
in the following series dealing with the effects of salts were propped open slightly 
with small pieces of cork. 
The solutions used were made up in water from the same source as that supplying 
the water in which the animals were living, so that they would be subject to no change 
in salt balance, excepting that change produced by the substance added. The 
analysis of the water with which the solutions were prepared is given in Table 11. 
Table 11 . — Analysis 2 of the water in which mussels live at Columbia, Mo. 
Per cent 
Calcium oxide 0. 00832 
Magnesium oxide . 00472 
Ferrous oxide . 00022 
Aluminum oxide . 00001 
Silicon dioxide . 00170 
Sulphur (computed as SO3) . 00552 
Chlorine .00194 
Each solution jar was constantly aerated by a stream of air bubbles from a com- 
pressed-air line, the air passing through water before entering the test solution. 
The mussels were changed to fresh solution every 24 hours, unless otherwise noted, 
to avoid the complications resulting from the accumulation of waste products in 
the solutions. Specific gravity and pH determinations were made regularly on the 
test solutions themselves as well as on the blood of the mussels in the solutions, to 
check against unexpected changes in the medium. As the test solutions, with the 
exception of the distilled-water series, did not show any significant change in either 
pH or specific gravity values, these determinations for the test solutions have not 
been included in the tables. Oxygen determinations by the standard Winkler method 
were also made on the various test solutions to ascertain if the aeration were ade- 
quate, and. as the oxygen values were all satisfactory they have not been listed. 
DISTILLED WATER 
For comparison with the responses to the various solutions of salts, several series 
of mussels were carried in distilled water, but otherwise under the same conditions 
as the animals in the salt-solution series. The data for these distilled-water tests 
are given in Table 12 and Figure 9. 
Various species of mussels were able to live in aerated distilled water for several 
days, but all showed a decline in sensitivity, and moribund individuals appeared 
during the first 24 hours. (Throughout the discussion of these experimental results 
“moribund” designates a mussel in which the heart had stopped beating when the 
shell was opened, but the animal was still responsive to tactile stimulation of the 
mantle margin or the foot.) 
It may readily be seen in Figure 9 that the specific gravity of the blood of all 
mussels living in distilled water was low, as nearly two-thirds of the cases lie below 
the line of average specific gravity (1.0026) for the blood of fresh-water mussels. 
This change in specific gravity came quickly, for at the end of the first 48 hours all 
! Figures from analyses made by department of physical chemistry, University of Missouri. 
