Inside the eye of many common fish, like tuna, scad, snapper, actually probably all fish I have eaten, is a small sphere made of some very tough substance. This sphere is even hard to crush with teeth, and seems to be made of homogeneous material. That is after the fish is cooked, not sure how it is uncooked. It is immersed inside a quite soft, almost liquid substance inside the eyeball.
Is that the lens, or is the whole soft semi-liquid tissue the lens?
What substance is the small tough sphere made of? I imagine some type of proteins, but what type of proteins exactly?