Introduction

The mammalian epididymis is part of the system of male accessory sex glands whose secretions constitute ejaculated seminal plasma (Mann & Lutwack-Mann, 1981). Unlike the other accessory glands, however, the epididymis is intimately involved with the development of spermatozoa from the moment they leave the testis to the point when they are ejaculated and deposited in the female tract. The basis for this statement is the large number of investigations carried out over many years on a wide variety of species, beginning with the pioneering experimental studies of Young (1929, 1931) on guinea pigs, which have enabled some basic principles to be established (Cooper, 1986; Orgebin-Crist, 1987). The molecular details of precisely how an infertile testicular spermatozoon is transformed into a fully fertile one in the epididymis are only slowly being unravelled and it is still not possible to pin-point any particular process or molecular component and say unequivocally that this is the crucial difference between fertility and infertility. The factors involved are almost certainly complex and interactive but there are enough experimental data to indicate that they exist and that the epididymis has an important regulatory role to play.

Despite the evidence alluded to above, and described in more detail below, a notion has arisen in recent years that in man the epididymis is relatively non-functional.