=Effect of glycerol additions on oxygen uptake of diluted semen at 37 deg. C.= The effect of adding glycerol to diluted semen on oxygen consumption of the sperm was tested in a Warburg apparatus, using semen diluted with an extender consisting of one part egg yolk and one part 2.9 percent sodium citrate dihydrate. The yolk-citrate extender was added to the semen at a rate which brought the sperm concentration in 0.5 milliliter to 200 million to 500 million. An exact count was used to calculate the oxygen uptake per 10^{8} sperm per hour (ZO_{2}). [Illustration: Effect of glycerol additions on oxygen consumption of sperm at 37 deg. C. (Fig. 9)] Glycerol in various percentages in 2.9 percent sodium citrate dihydrate solution was placed in the sidearm of the Warburg flasks. The diluted semen was held in the main compartment. After a 60-minute preliminary run, in which the rate of oxygen uptake of the sperm in yolk-citrate diluent was determined, the contents of the sidearm were tipped into the main compartment. The resulting glycerol percentages after mixing the sidearm and main compartment contents were 0, 4, 8, and 12 percent. Ten samples of semen were subsampled and the oxygen uptake of each was determined at all four levels of glycerol. Oxygen uptake was increasingly stimulated during the first 20-minute interval by each increase in the amount of glycerol added (Fig. 9). After the first 20 minutes, the rate of oxygen utilization decreased at the two higher levels of glycerol but persisted at 4 percent. The rate of oxygen consumption for the first 20-minute period at the 4-percent glycerol level was 130 percent that of the control to which only sodium citrate had been added. At 8 and 12 percent the values for the period were 144 and 192 percent, respectively, of the control rate. [Illustration: Effect of glycerol and glycerol-plus-catalase additions on sperm motility during incubation at 37 deg. C. (Fig. 10)] With each increase in glycerol level, motility was reduced during the incubation period. This is shown in Figure 10 along with the effect on motility of adding catalase, which is discussed in the next section. =Effect of glycerol-plus-catalase on oxygen uptake of diluted semen.= Certain bacteria have been shown to break glycerol down, forming hydrogen peroxide as follows: Glycerol + oxygen --> lactic acid + hydrogen peroxide.