Epididymal contents were collected from a bull with an epididymal fistula and from normal bulls after slaughter. When this material was diluted with seminal plasma collected by means of an artificial vagina from either the bull with a fistula or from normal bulls, the impedance change frequency due to the motility of the spermatozoa was reduced as was the length of time for which it could be detected. The fluid obtained from the penis of the bull during electric stimulation with a low voltage did not produce the same effect. The latter fluid had no fructose, a low protein content and a different pattern of inorganic ion concentration from the seminal plasma; the agar gel electrophoresis pattern was also different.
Dilution of epididymal contents with normal seminal plasma did not affect the morphology of spermatozoa or their response to differential staining. Furthermore, neither these characteristics nor the impedance change frequency were affected by a mild degree of temperature shock produced by sudden cooling from 20° C to 10° C.