The oxygen consumption of human spermatozoa has been determined polarographically with Clark electrodes both in whole semen and in a buffered Ringer solution. Washing of the spermatozoa caused an average decrease of 13% in the number of live cells. The oxygen consumption of the spermatozoa was two to three times higher in the Ringer solution than in the whole semen (P<0·001).
If the washed spermatozoa were returned to their own seminal plasma, the oxygen consumption also returned to the original level. These results indicated that human seminal plasma normally contains a factor that depresses sperm respiration.