1. The rabbit neurohypophysis is composed of nerve fibres and their endings, of neuroglia and microglia, and of a vascular system with reticulin fibres spreading in perivascular spaces.
2. The nerve tracts in the pars nervosa lie in the wide areas between the perivascular spaces, but the axons leave the tracts to run their terminal courses within these spaces.
3. The axons terminate in complicated giant bulbs and menisci.
4. The neuroglia lies in the same areas as the nerve tracts. Many neuroglial processes cross the perivascular spaces and end in attachment to the vessel wall. There are no important connexions between neuroglial cells and axon endings.
5. There is no specific type of neuroglia peculiar to the neurohypophysis. The morphology of the neuroglial cells in the median eminence and in the stalk is different from that of the neuroglial cells in the pars nervosa.
6. Morphologically, the neurohypophysis appears to be a sensory organ, similar to the chemo-receptors and pressor-receptors existing in other parts of the body. If it has a secretory function as well, then the secretion may occur at the giant terminations of the nerves, perhaps by a process of rupture of these formations.