1. A formaldehyde-induced fluorescence characteristic of norepinephrine was demonstrated in numerous adrenergic nerve terminals, vascular as well as non-vascular, in the follicle wall.

2. Electron microscopy of glutaraldehyde-osmium-fixed tissue showed the presence of non-vascular smooth muscle-like cells—characterized by myofilaments, dense bodies and micropinocytotic vesicles —arranged in groups within the theca externa. The cells were closely related to each other (only about 30-100 nm distance between adjacent cells) and had a direction essentially parallel to the surface.

3. Electron microscopy also revealed bundles of non-myelinated nerves in the stroma issuing branches in among the smooth muscle-like cells as well as to muscular blood vessels. Close to the smooth muscle-like cells the nerve terminals were partly devoid of Schwann cell ensheathing and reached as close as 50 nm to the membrane of the cells.

4. With regard to the appearance of the synaptic vesicles (30-70 nm in diameter) in the axon varicosities there is reason to assume that the nerves to the smooth muscle-like cells are both of adrenergic and cholinergic type.

5. Tyramine produced a dose-dependent contraction of isolated strips from the follicle wall. The effect was potentiated by previous exposure to norepinephrine and this potentiation was inhibited by cocaine which blocks the uptake of added norepinephrine into the nerves. This confirms the presence of adrenergic nerves which can release norepinephrine to produce a contraction in the follicle wall.