Death and the Maiden & Thoughts on Appreciating Art

Edvard Munch, Death and Life, 1894
(Also titled as Death and the Maiden)

I have seen Munch's Death and Life several times before but I never knew until just now that what is depicted on the left is a stream of sperms. (See here, click on Details.) This is a difficulty I experience repeatedly in my pursuit of appreciating art properly... how can one ever know such things about a work by just looking at the image, when, once known, it is apparent that such facts are crucial to a proper appreciation of the painting? Appreciating art, it seems, entails more than just looking at the painting; it also requires reading and researching about it.