Note 64 — Chapter II · THE ANT-EATERS.
Reading edition
The muscle called pronator quadratus is a fleshy band, four-sided in shape more or less. One side is attached to one of the bones of the fore-arm, the ulna in front above the wrist; and the other and opposite side adheres to the radius. The ulna being motionless, the muscle contracts and pulls the radius over, so as to turn the back of the wrist forwards, or upwards. The prone position is thus produced, and hence the name of the muscle. The other muscle which produces this movement is fixed to the fore-arm in front, near the inner elbow, and it is long, having a tendon which is implanted on the radius. As this muscle contracts, it pulls the radius over the ulna, and makes the wrist take up a prone position. It is called the pronator teres.