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Vasa deferentia of 20 human adult males and 8 children were divided into four portions (proximal, middle, distal and terminal) for histological, histochemical and ultra-structural studies. The epithelium of the adult vas deferens was formed of columnar and basal cells. Three types of columnar cells were observed: (1) principal cells with PAS-positive cytoplasmic granules (lysosomes); (2) dark or pencil cells with a dark cytoplasm and nucleoplasm and cytoplasmic lipid vacuoles, and (3) mitochondrion-rich cells with numerous mitochondria similar to those of principal cells. All these cell types showed stereocilia and irregular convoluted nuclei, some of them containing granular, PAS-positive intranuclear inclusions. Principal cells were the most frequent cell type in the proximal portion but their number gradually decreased along the length of the vas deferens, while the proportion of both pencil cells and mitochondrion-rich cells increased. The muscular coat comprised three muscular layers: (1) inner longitudinal, (2) middle oblique (circular in the distal and terminal portions), and (3) outer longitudinal. The functional significance of regional variations is discussed. The infant vas deferens showed a columnar cell type only. However, cells either with numerous lysosomes or with numerous mitochondria were occasionally found. No regional variations were observed in the infant vas.

Normal (infant and adult) and pathological testes were examined by electron microscopy in order to study testicular innervation. Nerves composed of non-myelinated fibres were abundant in the tunica vasculosa of the tunica albuginea. These nerves penetrated into the testicular septa reaching the interstitial tissue. This showed numerous non-myelinated nerve fibres running among the Leydig cells and blood vessels. Single axons or small groups of them, partially surrounded by Schwann cells, approached: 1) the Leydig cells, 2) the interstitial blood vessels, and 3) the seminiferous tubules. Single naked axons were also observed primarily in the proximity of the seminiferous tubules. These axons showed varicosities containing both small and large "synaptic" vesicles. The latter were less numerous and contained a central dense core. Small vesicles were agranular. Some varicose axons ran across the myofibroblast layer of the tunica propria reaching the basal lamina of the seminiferous tubules at the level of the Sertoli cells but not at the level of the spermatogonia. The intercellular space between Sertoli cell and axon membrane was about 150-200 nm.

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