An otoacoustic emission (OAE) is a sound which is generated from within the inner ear. Having been predicted by Thomas Gold in 1948, its existence was first demonstrated experimentally by David Kemp in 1978 and otoacoustic emissions have since been shown to arise through a number of different cellular and mechanical causes within the inner ear. Studies have shown that OAEs disappear after the inner ear has been damaged, so OAEs are often used in the laboratory and the clinic as a measure of inner ear health.
There is a lot to like about The Nourishing Traditions Book of Baby and Child Care by Sally Fallon Morrell and Thomas S Cowan. Some of it is exceptionally well-researched (other things I thought were a little sketchy or questionable, see further below). I could never list all the awesome things the book discusses, but some of the highlights for me include: