GLUCOSE AND OXYGEN UTILIZATION IN SYMPATHETIC GANGLIA 93 



1942) is used to measure the amount of oxygen remaining in a solution which 

 has been pulled past the experimental tissue at a known rate. The essential 

 glassware of such a respirometer, made to fit the superior cervical ganglion of 

 an adult rat, is shown in Fig. 3. 



During an experiment, the reservoir on the left was closed at the top by a stopper and 

 was filled with a bathing solution continually equilibrated with 95% O2 , 5% CO; . The fluid 

 was pulled through the respirometer by two motor-driven syringes connected to the ball and 

 socket joints on the right. The ganglion was placed in the expanded upper portion of the 

 vertical tube, with the postganglionic nerve pulled into the small channel in the ground glass 

 plug at the top and the preganglionic nerve pulled down through the narrow channel below, 

 so that its end lay in the lower expansion. Stimuli were applied between two platinum wires 

 with tiny ball tips sealed through the glass plugs at the bottom and at the right. The pre- 

 ganglionic action potential could be recorded between a platinum electrode (not shown) which 

 dipped into the reservoir on the left and a calomel cell (also not shown) which was connected 

 to the bathing fluid beyond the upper ball joint. The postganglionic action potential was 

 recorded between the same calomel cell and the platinum wire at the top. The electrode used 

 for measuring oxygen concentration passed through a stopper inserted in the receptacle at 

 the upper right, with the tip of the electrode lying in the small tube leading fluid away from 

 the ganglion. Solution which passed the stimulating electrodes was carried away by the lower 

 syringe, so that the oxygen measurements, which were made in the upper outflow, were not 

 affected by events at the stimulating electrodes. 



All the parts shown in Fig. 3, and also an assembly of stopcocks and flasks for changing 

 solutions, were sterilized in an autoclave. In addition the bathing solutions were sterile and 

 the ganglion was excised and inserted in the respirometer aseptically. These precautions were 

 necessary because the ganglion was so small that under non-sterile conditions the empty 

 chamber and the solutions flowing through it were sometimes found to consume about as 

 much oxygen as the tissue itself. The whole apparatus was placed in a temperature-controlled 

 box. An experiment lasting many hours, including changing of solutions, was performed 

 without opening the box. 



Fig. 4 shows a record of oxygen concentration in the solution leaving the 

 ganglion. Oxygen concentration increases downwards in this record; the level 

 for zero oxygen is considerably above the top of the figure. The oxygen scale 

 has been thus inverted in order to make an upward deflection represent an 

 increase in rate of consumption: obviously the faster the consumption, the less 

 oxygen remained in the solution. The sudden descents shown in the record 

 occurred when fluid was pulled past the tissue at an accelerated rate which was 

 so fast that only a negligible amount of oxygen was removed from the solution. 

 This was done for purposes of calibration and indicated the line of zero oxygen 

 consumption. The rest of the scale, shown at the left of the illustration, could 

 then be calculated, knowing the flow rate, the solubility of oxygen, and the 

 weight of the tissue. At the arrow in this illustration the bathing fluid was ex- 

 changed for one containing sodium azide. After some brief and largely arti- 

 factual disturbances the rate of oxygen consumption fell, a well-known effect 



