EXPERIMENTAL STUDY OF THE OYSTER GILL 



II 



The large tank is filled with water up to the level of the vertical tube c. When 

 equilibrium is established the rubber tube inserted into the oyster is connected to 

 the horizontal tube b and the water from the gills begins to flow into the small 

 vessel. The overflowing water is collected in a graduate. , 



The hydrostatic pressure inside the gill cavity can be measured by plugging the 

 vertical tube c and watching, in the water gauge (g), the rise of the level in the small 

 vessel. In a few minutes a maximum difference is reached and the flow of water 

 through the tube b ceases. This indicates that there is no more difference in pressure 

 between the inside of the gill cavity and the end of the tube b. 



Fig. 2. — Tank for collecting the water after it passed through the gills, and measuring the hydrostatic pressure inside the 

 gill cavity. 6. — tube coimecting the two vessels; c. — overflow; g. — water gauges; I. — constant level arrangement; 

 p.— pipe supplying fresh sea water; (.—thermometer. .Approximately one-third natural size 



The difficulty in employing the tank method lies in the necessity of being very 

 careful to keep the water in both vessels at a constant level. The rise of level in the 

 large tank forces the water to flow by gravity through the gills, while a rise in the 

 level in the small vessel retards the rate of flow because the gill epithelium is forced 

 to work against the pressure. The method is indispensable, however, for collecting 

 the water that had passed by the gills. 



CARMINE METHOD 



The rate of flow of water can be determined easily by the carmine method (Galt- 

 sofl, 1928), which is as follows: The oyster is rigged up in the same manner as in the 



