In the maturing testis, the cranial region is spermatogenic
(Fig. 2), the medial region is both spermatogenic
and secretory (Fig. 3), and the caudal region is strictly
secretory (Fig. 4). The secretion reacts positively to the
PAS and ninhydrin-Schiff techniques, which indicates
the presence of neutral glycoproteins. In the resting testis
(Fig. 5), this secretion is absent (Figs 6, 7), and the lumen
of the tubules becomes occluded.