Keel (bird anatomy) Keel (bird anatomy) A keel or carina (plural carinae) in bird anatomy is an extension of the sternum (breastbone) which runs axially along the midline of the sternum and extends outward, perpendicular to the plane of the ribs. The keel provides an anchor to which a bird's wing muscles attach, thereby providing adequate leverage for flight. Keels do not exist on all birds; in particular, some flightless birds lack a keel structure. Historically, the presence or absence of a pronounced keel structure was used as a broad classification of birds into two orders: Carinatae (from "carina", "keel"), having a pronounced
Answering the Question: What is Enlightenment? II of Prussia for creating these preconditions. Kant focused on religious issues, saying that "our rulers" had less interest in telling citizens what to think in regard to artistic and scientific issues. Kant answers the question in the first sentence of the essay: "Enlightenment is man's emergence from his self-incurred immaturity (Unmündigkeit)." He argues that the immaturity is self-inflicted not from a lack of understanding, but from the lack of courage to use one's reason, intellect, and wisdom without the guidance of another. He exclaims that the motto of enlightenment is "Sapere aude"! – Dare to be wise! In the