Sometimes you only see what you're looking for

The title will be a truism to any woman feeling broody.  As soon as the idea is in your head, the only women in the world are pregnant women.  But it has broader applications as well, as I found to my cost today in the London Library.  I was browsing the section on Birds, looking more in hope than certainty, for a book on the mythology of ravens, crows or rooks.  And suddenly, there it was, staring at me: "The Mythology of the Raven".  I settled down in the reading room but after a puzzled few minutes flicking through pictures of dissected birds and diagrams of muscles I looked again at the title.  And learnt a new word: myology.