According to Wakeley (1943-44), the majority of epididymal cysts in man arise in the vasa efferentia, the bridge of tissue between the testis and epididymis. The ability of two sterilant chemicals to produce specific lesions of this nature in the rat (\g=a\-chlorhydrin\p=m-\Ericsson,1970; ethylenedimethanesulphonate\p=m-\Cooper & Jackson, 1970) points to the need for further information on the vasa efferentia in relation to their susceptibility to damage in this manner. As there appears to be inadequate information on the course of these tubules, the present study was undertaken.At post mortem, the testes resting in the scrotum of the rat present anterior and posterior surfaces and medial and lateral rounded borders. Serial longitudinal sections were made in both rat and mouse of the entire testis-epididymisvas complex, from the anterior to the posterior surface. In sections from a number of rats, it was observed that the rete testis penetrates into the tunica albuginea and from it, two channels of vasa efferentia emerge (Pl. 1 , Fig. 1); the arrangement is similar in the mouse (Pl. 1, Fig. 4). In the rat, both tubules become convoluted in relation to a non-tortuous artery and vein, which are branches of the superior epididymal vessels. The two channels and the blood vessels ascend in a column of fat covered by a peritoneal layer, inclining slightly laterally and posteriorly. In its ascent, each passes behind the caput epididymidis to a variable distance above it. There, the tubules arch medially and anteriorly (the arch, PI. 1, Figs. 2 and 3) and gain the upper margin of the proximal caput into which the vasa efferentia become incorporated (PI. 1, Fig. 3). It is at the arch that the nutrient vessels join the tubules from the lateral aspect. The vasa efferentia are relatively large at their origin from the rete testis (PI. 2, Figs. 5 and 6) and become smaller as they approach their union with the caput. A single layer of cubical to columnar epithelium supported by delicate fibres forms the wall, while stroma envelops them. Invariably, the vasa are empty in sections of normal specimens.According to Cunningham (1928), the vasa efferentia of the rat leave the testis, pass dorsal to the epididymis and join the anterior lobe of the caput. Harrison (1953)

The antifertility effects and histopathological changes in the reproductive tract of male rats following administration of \g=a\-chlorohydrin, \g=a\-bromohydrin,epi-chlorohydrin and glycidol were compared. Contrary to earlier reports, \g=a\-bromohydrin induced bilateral spermatocoeles and permanent sterility in rats but did not produce the functional epididymal sterilizing effect of \g=a\-chlorohydrin.Glycidol reproduced the primary sterilizing effect of \g=a\-chlorohydrin but not the lesions in the proximal caput epididymidis. Epi-chlorohydrin showed activities resembling those of \g=a\-chlorohydrin. The primary lesion in the proximal caput epididymidis was seen specifically to involve the`conus' and adjacent regions with sloughing of the epithelium. This may impair the secretory/absorptive function of this region with ensuing severe damage to the thin-walled ductuli efferentes. Except where granulomata were formed, restoration of the epithelium occurred. The apical region of the proximal caput remained undamaged throughout.

Histological changes in the rat testis were correlated with the antifertility effects of injections of three diol diesters of methanesulphonic acid. The compounds are consecutive members of a homologous series each differing by -CH2-from its neighbours. The diester of ethylene glycol (EDS) caused antispermatogenic effects resembling those following hypophysectomy and was associated with involution of prostate and epididymis; spermatocoele formation occurred in the latter organ. Methylene dimethanesulphonate and 1,3-propylene dimethanesulphonate induced changes consistent with spermatogonial damage resembling those produced by Myleran (busulphan).

Summary. The

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