RESUMEN
The functional organisation of the epididymis has been studied in 20 adult albino rats. The gross divisions of Caput or head, Corpus or body, and Cauda or lower end show distinctive features which indicate functional specialisation. The Caput epididymis has strikingly tall columnar cells with a mean height of 124 mu, but little muscle tissue. It seems to be adapted as a distensible low-pressure reservoir to accomodate the testicular outflow and modify it by absorption and secretion; the prominent stereocilia (or microvilli) would favour this absorptive function. The Cauda, on the other hand, shows abundant muscle tissue around the widening duct and provides the mechanism for rapid delivery of sperms during ejaculation. The Corpus or middle part is peculiarly long and slender, accomodating only 2 or 3 ductules side-by-side. It might serve to separate the two functionally different upper and lower parts and protect the testis against any undue back-pressure. The epididymis weighed 67% of the corresponding testis, on an average. The capacity of the testis to tolerate any obstruction of the outflow tract might be related to the size and capacity of the epididymis in that species.