The slight depression in the retina in the axis of the globe is the fovea centralis, or yellow spot; the optic nerve pierces the ball to its inner or nasal side. The lens, with its suspensory ligament, separates the aqueous from the vitreous humour. On the front of the lens rests the iris, covered on its posterior surface with black pigment. On either side of the lens is seen a ciliary process, with the circular fibres of the ciliary muscle cut transversely, and its radiating fibres disposed as a fan.