This highly coiled testicular artery within the bovine spermatic cord has a constant luminal diameter but a continuously decreasing mural thickness. The pampiniform plexus is composed of three interconnected venous networks differing in mesh sizes and calibres. The large veins of the first network display pouches and permanent constrictions, which may serve as throttle devices. The constitutents of the third network are venules or venous capillaries with diameters between 10 and 20 micron; they favor a periarterial position or even occupy the media-adventitia border of the testicular artery. All plexus veins are devoid of valves. The existence of true arteriovenous anastomoses between smaller branches of the testicular artery and plexus veins was established by serial sections. The vascular morphology of the spermatic cord is discussed with special attention to a postulated venous-arterial steroid transfer in this region.

The bovine testis has a central mediastinum consisting of longitudinally oriented rete channels and spacious lymph vessels, embedded in the mediastinal stroma. The latter represents a contractile-elastic unit and is composed of myofibroblasts, collagen bundles and accumulations of elastin, connecting the myofibroblasts. The dimension of the mediastinum varies in cross sections at different levels between 3.5 and 31.8 mm2. In one cross section approximately 30 rete channels and approximately 30 openings of straight testicular tubules are encountered. Nearly 25% of the area is occupied by thin-walled, valveless lymph vessels. Arterial convolutes, interpolated between straight centripetal and straight centrifugal branches of the testicular artery flank the rete on all sides. It is concluded that the pulsation within these convolutes together with the contractile-elastic stroma promotes lymph and rete content in a caudo-cranial direction. Chordae retis as described by Roosen-Runge and Holstein (1978) for the human testis are a common feature in the bovine mediastinum testis. The rete channels are lined by a simple cuboidal or columnar epithelium. Short intraepithelial crypts are present and function as epithelial reserve for dilatation and expansion of the rate. The inventory of organelles is rather inconspicuous in the rete epithelium. The apical border bears short microvilli and gives a strong reaction for alkaline phosphatase. The basal cytoplasm contains many small to medium-sized electron-dense bodies and is site of a strong acid phosphatase reaction. The rete epithelium as a whole reacts strongly with leucine aminopeptidase, the marker enzyme of the testicular excurrent duct system. Many free mononuclear cells, mostly macrophages, are observed in the basal half of the rete epithelium.

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