he gives to the opposite leg all the rest of the bulk of the whole man, including [the weight of] the other leg; he then raises the other leg and sets the foot upon the step to which he wishes to raise himself. Having done this he restores to the upper foot all the weight of the body and of the leg itself, and places his hand on his thigh and throws his head forward and repeats the movement towards the point of the upper foot, quickly lifting the heel of the lower one; and with this impetus he lifts himself up and at the same time extends the arm which rested on his knee; and this extension of the arm carries up the body and the head, and so straightens the spine which was curved.
[32] The higher the step is which a man has to mount, the farther forward will he place his head in advance of his upper foot, so as to weigh more on a than on b; this man will not be on the step m. As is shown by the line g f.
[Footnote: See Pl. XXIII, No. 1. The lower sketch to the left belongs to the four first lines.]
376.
I ask the weight [pressure] of this man at every degree of motion on these steps, what weight he gives to b and to c.
[Footnote 8: These lines are, in the original, written in ink] Observe the perpendicular line below the centre of gravity of the man.
[Footnote: See Pl. XXIII, No. 2.]
377.
In going up stairs if you place your hands on your knees all the labour taken by the arms is