The Da Vinci Notebooks at sacred-texts.com
From the top of the shoulder to the point of the elbow is as far as from that point to the joints of the four fingers with the palm of the hand, and each is 2 faces.
a e is equal to the palm of the hand, r f and o g are equal to half a head and each goes 4 times into a b and b c. From c to m is 1/2 a head; m n is 1/3 of a head and goes 6 times into c b and into b a; a b loses 1/7 of its length when the arm is extended; c b never alters; o will always be the middle point between a and s.
y l is the fleshy part of the arm and measures one head; and when the arm is bent this shrinks 2/5 of its length; o a in bending loses 1/6 and so does o r.
a b is 1/7 of r c. f s will be 1/8 of r c, and each of those 2 measurements is the largest of the arm; k h is the thinnest part between the shoulder and the elbow and it is 1/8 of the whole arm r c; o p is 1/5 of r l; c z goes 13 times into r c.
186:171 : See Pl. XX where the text is also seen from lines 5-23.