Dissecting Leonardo's Anatomy
 

The Heart The Lungs (and Respiratory System)

The Heart and Respiratory System On the heart: "Heart open in the receptacle of the spirits, that is in the artery; and in M it takes or rather gives the blood to the artery, and by the mouth, B, it refreshes itself with the air form the lung, and by C it fills the auricles of the hearts. Of the heart. This moves of itself and does not stop unless for ever " (qtd. in MacCurdy 119).                                                         On the respiratory muscles: "These muscles have a voluntary and an involuntary movement seeing that they are those which open and shut the lung. When they open they suspend their function which is to contract, for the ribs which at fist were drawn up and compressed by the contracting of these muscles then remain at liberty and resume their natural distance as the breast expands. And since there is no vacuum in nature the lung which touches the ribs from within must necessarily follow their expansion; and the lung therefore opening like a pair of bellows draws in the air in order to fill the space so formed" (qtd. in MacCurdy 102).