The unobservant student too often makes the lower arm look like the neck of a bottle, making it taper too suddenly towards the hand—the subtle curvatures of the arm are overlooked.
I have made a few drawings of the arm, just to show the general tendencies of the upper and the lower parts of the limb.
The points to consider are indicated by the marks against the outlines in three of the drawings, where the highest swellings of the lines are to be found, on the opposing sides.
In Nature these highest swellings are rarely seen exactly opposite each other, and this variation accounts for the curvatures already alluded to.
In the placing of the hand on the wrist, mark carefully the relative position of the protuberances on the one side and concavities on the other.