In recent years, it has become apparent that the testis produces, in addition to the androgens, considerable amounts of another type of secretion which flows from the lumina of the seminiferous tubules through the rete testis into the epididymis. Here a large part of the fluid part of the secretion is reabsorbed, but additional compounds are added as the spermatozoa pass down the epididymal duct. In this paper, attention will be largely confined to the most recent findings concerning this latter secretion, as the earlier observations have been reviewed by Setchell (1970a) and Setchell & Waites (1971).
Rate of flow and ionic composition
The fluid which flows from the rete testis of all species so far examined (ram, bull, boar, rat, hamster, wallaby) is a low-protein fluid, isotonic with plasma but containing about three times as much potassium, less sodium and bicarbonate and more chloride than plasma or testicular lymph.