522 
BULLETIN OF THE BUREAU OF FISHERIES 
melting the surface of the wax and pressing the shell, which had previously been 
wiped dry with a cloth, into the beeswax just before it hardened. In this way it 
was possible to suspend the mussel in the water at any desired depth or angle and 
hold the animal stationary; but at the same time the movements of the foot, gills, 
and other soft parts were not interfered with in the least, as the mussel could open 
and close its valves at will. (It may be noted here that this method has proved 
very satisfactory for several types of experiments and individual mussels have been 
observed continuously for over three months while attached to beeswax blocks as 
described.) 
From the experiments on the activity of the foot-margin (to be reported in 
detail elsewhere) it was found that the margin of the foot is kept in constant motion 
regardless of the position of the foot and whether it be expanded or retracted, and 
that two rhythms are maintained- — that is, there are large contraction waves on 
which smaller or faster contraction waves are superimposed. These movements of 
the foot serve not only as part of the locomotion complex, but they produce currents 
in the water in the vicinity of the foot and in that way aid both respiration and the 
taking of food. 
As these movements continue so regularly and are associated with vital activities 
of the mussel, they were used to verify the salt concentrations of the blood as deter- 
mined by the analyses. 
It is well established that strips of muscular organs may be removed from the 
bodies of various animals, and, when mounted properly, these pieces of organs will 
continue to display normal activity for many hours. As the muscular foot of the 
fresh-water mussel forms the outer portion of the visceral mass of the animal (see 
fig. 7) almost the entire foot may be removed by cutting along the line of junction 
of the foot and viscera. In this way a “foot strip” could be prepared free from all 
other organs and including almost all of the foot muscle. 
Such strips of living tissue from other animals are customarily mounted in the 
blood serum of the animal from which they were taken or in some fluid containing 
the principal salts of the blood in the proper proportions, so that strips which have 
been separated from their connections with the circulatory system may obtain from 
the fluid in which they are immersed the essential salts or other substances which 
they would have received from the blood. 
In order to test the validity of the normal values which were obtained from the 
various analyses of mussel blood, such a fluid was compounded containing the prin- 
cipal salts found in mussel blood in the proportions determined by these analyses, 
and the whole adjusted to the average pH value for mussel blood. This fluid because 
of its similarity to the “Ringer’s fluid” commonly used for studies of vertebrate 
tissues, was designated “unionid ringers,” and the formula is given in the following 
table : 
Table 10. — Composition of unionid ringers fluid in which mussel tissues maintain normal activity 
Per cent 
Sodium chloride 0. 153 
Calcium chloride . 012 
Potassium chloride . 015 
Magnesium chloride . 010 
Di-basic sodium phosphate . 009 
Sodium bicarbonate, to adjust the pH value to pH 7.9. 
