Hippomanes

[1] Hippomanes arise from unconsumed and thickened nutrient fluid (histiotrophe) of the placenta, in concentric layers around the centre of allantoic calculi of tissue debris.

[1] The chemical composition is different to amniotic fluid, which along with the insolubility suggests that it's not a result of a simple precipitation process, but a denatured mucoprotein complex.

[1] According to Pliny the Elder,[7] the Hippomanes, which are said to be found as tough bodies on the forehead of the newborn foal, are eaten by the mare immediately after birth.

If the mare was prevented from doing so, she would feel no affection for the foal and refuse to feed it, which is why it was believed that the power of love was concentrated in the hippomanes.

[8][9] In a Greek mythology tale, Glaucus, the son of Sisyphus, is devoured by his horses at the funeral games for Pelias, the father of Acastus, during the chariot race, because Aphrodite had driven them wild with Hippomanes.