1. The nictitating membrane also covers the eye and acts as a contact lens in many aquatic birds.

2. The Beaver's eyes have a thin, transparent membrane, called a nictitating membrane, which is pulled over the eyeball for underwater work

3. In comparison with noradrenaline the pressure effect is reduced after adrenalectomy and cocaine; an increased sensibility of the blood pressure and the nictitating membrane to adrenaline and noradrenaline and less pronounced to tyramine; an inhibition of the adrenergic neuron function, demonstrated at the nictitating membrane, the peripheral splanchnic nerve stimulation and the blood pressure action of a nicotine-like substance.

4. Distinct nicotine antagonistic and local anaesthetic properties are also present. a sympathomimetic action, visible in a rise of the arterial blood pressure and a contracture of the nictitating membrane.