The ground substance of the testis of the albino mouse is PAS-positive but not metachromatic, and probably highly aggregated. The basement of the seminiferous tubules is intensely PAS-positive, metachromatic, and possibly not so highly aggregated.
The reactivity of the ground substance to the PAS reaction and toluidine blue is tentatively ascribed to the presence of chondroitin sulphate C: this compound, previously known to contain N acetyl-galactosamine, glucuronic acid, tyrosine and tryptophane, is associated with arginine.
The genesis of the basement membrane of the seminiferous tubule is shown to include the formation of a sheath of atypical elongated fibroblasts, the secretion of a PAS positive, metachromatic substance associated with arginine between this sheath and the seminiferous tubule, the appearance of mitochondria in the cells of the sheath, and lastly, the acquisition of alkaline phosphatase by these fibroblasts and its spread to the intervening ground substance. These changes are thought to be related to the structural and nutritional requirements of the seminiferous tubules.
In its intense positive reaction to PAS and in its metachromasy, the basement membrane of the seminiferous tubule agrees with the ground substance adjacent to sites of active protein metabolism, such as growing tumours, embryonic organs, hair follicles, and skin.