OXYGEN CONSUMPTION OF OYSTEKS 
491 
adductor muscle, and small glass rods were inserted to hold the shells open. It was 
found, however, that frequently the glass rods were expelled. This indicated that the 
presence of a foreign body stimulated the contractions of the adductor muscle which 
in turn affected the amount of oxy- 
gen consumed. To obviate this diffi- 
culty another method was devised, 
whereby determinations were made 
on single oysters, mounted as de- 
scribed below, so that the opening 
and closing of the shell was recorded 
on a kymograph. 
Two methods were used for the 
determination of oxygen consump- 
tion. In the first method, which in 
the following discussion is referred 
to as a closed chamber method, six 
oysters, the shells of which were kept 
apart by glass rods, were placed in 
apparatus similar to that used by 
Bruce (1926). (Fig. 1.) Itconsisted 
of a 14-inch diameter heavy glass 
desiccator with ground glass flanges 
held together with clamps and a rub- 
ber stopper on the top of the dome- 
shaped lid. Three glass tubes were 
arranged in the stopper; one, extend- 
ing to 1 inch above the bottom, 
formed a syphon outflow ; the second 
one ended just below the stopper and 
served for replenishing the water 
when a sample was being taken; 
through the third one, filled with 
paraffin oil, passed the stem of the 
stirrer. By simultaneously regulat- 
ing the outflow and the inflow of the 
water, a sample was withdrawn and 
the water in the chamber replenished 
from a reservoir containing filtered 
sea water of a known oxygen con- 
tent. The chamber was kept in a 
constant temperature bath. 
In the second method, which in 
the following discussion is referred to 
as open chamber method, the deter- 
minations of oxygen consumption 
were made on single oysters, the valves of which were connected to a recording lever of 
the kymograph. An oyster was placed in a 2-liter open jar filled with sea water. To 
prevent the exchange of gases between the air and the water the latter was covered with 
Figure 1 .— Closed chamber for the determination of oxygen consump- 
tion. A, Glass stirrer; B, inlet; C, outlet; D, ground glass flanges 
on cover and base held together with clamps; E. oysters held open by 
means of small rods inserted between the' valves; G, glass tubing in 
which stirrer rotates, sealed with paraffin oil; P, paraffin oil; R, rubber 
stopper 
