Amnion

Amnion [amnion – JNA (The anatomic nomenclature Yenskaya), LNH (The Leningrad histologic nomenclature) of LNE (The Leningrad embryological nomenclature); synonym: kloketova partition; Greek amnion – amnion, a fetal membrane; synonyms: an amniotic bag, an amniotic cover, a water cover] – a protective cover which is formed around a germ of the highest vertebrata by accretion of a parietal layer of a mesoderm and folds of an ectoderm.

 
Whether you know that:

Having fallen from a donkey, you more likely will kill yourself, than having fallen from a horse. Only do not try to disprove this statement.