Centimeters 



Figure 184. — Metabolism chamber, details ot construction. A — oyster resting on heavy concrete base ready for me- 

 tabolism test; B — inlet for sea water of known oxygen content; C — outlet; D — lead bars; E — slanted removable top 

 underlined with a rubber gasket; F — clamps; G— rubber balloon which serves as a flexible gasket for test tube H 

 which rests on the valve of the oyster; I — laboratory brush inserted into the test tube and attached to the writing 

 lever of a kymograph. 



small rubber balloon G tied with a silk thread 

 acts as a fleyible, watertight gasket witii enough 

 slack to permit slight vertical movements of the 

 tube as the oyster opens and closes its valves. 

 The connection with the writing lever of a kymo- 

 graph is made by inserting a small laboratory 

 brush in the glass tube and attaching the metal 

 handle of the brush to the arm of the lever (fig. 

 183). Outlet C is connected to the tubing which 

 leads to collecting cylinders K (fig. 183). The 



chamber without oyster must be checked first by 

 taking simultaneous samples of water from the 

 control and from one of the collecting cylinders. 

 When the samples give identical values of oxygen 

 content a second test is made with the closed 

 oyster in place in the respiratory chamber. If the 

 difiference in the two samples exceeds the probable 

 titration error, a search for trouble should be 

 made. Usually it can be traced to a defective 

 paraffin coating of the shell or to the growth of 



TRANSPORT OF WATER BY THE GILLS AND RESPIRATION 



203 



