İKİNCİ FEN · ÜÇÜNCÜ BÂB · İKİNCİ FASIL · Dördüncü Madde
Fourth Article
Concerning the muscles and movements of the wrist.
O esteemed one! Know that anatomists have stated: The wrist joint is moved by some muscles which abduct, others which adduct, some which move outwards, and others which draw inwards.
Some of the muscles that effect the extension of the wrist are closely joined [125/b] – one originates from the middle of the lower zone (zend-i esfel), extending to the veterinary thumb and moving it away from the index finger. Another arises from the upper ulna, attaching to the bone preceding the veterinary carpal bone, aligned with the thumb. When these two move together, they cause a slight pronation of the wrist. If only the second muscle moves, it releases the wrist outwards. If only the humerus moves, it both releases the wrist and holds the thumb away from the index finger. And there is another muscle which originates from the lower end of the humerus, crossing diagonally on the outer side of the upper ulna, and divides into two tendons. One tendon joins the bones of the index and middle fingers, while the other rests on the lateral side of the wrist upon the upper ulna, causing a slight pronation of the wrist and moving it away from the arm.
The flexor muscles of the wrist are a pair of muscles located on the outer side of the forearm. The lower portion of one originates from within the head of the radius and attaches to the bone before the little finger. Its upper portion arises above the carpal bone, again attaching to the aforementioned prominence. Another muscle originates from the lower end of the humerus, entering between the two muscles just described. It has two heads which intertwine like a cross, attaching to the region between the thumb and middle fingers. When these two move together, they cause flexion of the wrist. Thus, the extensor muscles being explained also effect constriction and relaxation (kabz and bast) upon it.
If the muscle attached to the prominence before the little finger moves alone, it turns the palm inwards a slight amount towards the back of the hand. If the muscle of the thumb, which will be explained, assists this muscle, it completely rotates the palm. If the muscle attached to the wrist before the thumb moves alone and is active, it turns the palm inwards a slight amount towards the face. If the muscle of the little finger assists in this, it completely rotates the palm.
“[We] glorify Allah, who has perfected and operates all of this.”