Of the cause of breathing, of the cause of the motion of the heart, of the cause of vomiting, of the cause of the descent of food from the stomach, of the cause of emptying the intestines.
Of the cause of the movement of the superfluous matter through the intestines.
Of the cause of swallowing, of the cause of coughing, of the cause of yawning, of the cause of sneezing, of the cause of limbs getting asleep.
Of the cause of losing sensibility in any limb.
Of the cause of tickling.
Of the cause of lust and other appetites of the body, of the cause of urine and also of all the natural excretions of the body.
[Footnote: By the side of this text stands the pen and ink drawing reproduced on Pl. CVIII, No. 4; a skull with indications of the veins in the fleshy covering.]
Taken from The Notebooks of Leonardo da Vinci edited by Jean Paul Richter, 1880.