İKİNCİ FEN · ÜÇÜNCÜ BÂB · İKİNCİ FASIL · Üçüncü Madde
Article Three
Concerning the muscles and movements of the forearm.
O, esteemed one! Know that anatomists have said: Some of the muscles which move the forearm open it, others hold it. They are situated upon the arm bone. Some encompass the arm bone in accordance with its form. Some turn the arm so that the palm of the hand faces downward, and some turn the arm so that the palm of the hand faces upward. These muscles are not upon the arm bone. However, the extensor muscles of the forearm are a fence-like group; one pair of which inclines inward, opening and extending the forearm from the shoulder. For one of these muscles originates beneath the front side of the arm bone and from the lower rib of the shoulder, terminating in the inner aspects of the elbow. The second is directed outward, causing supination and extension of the forearm. For this muscle arises from the head of the arm bone, reaching the outer aspects of the elbow. When these two muscles are drawn together, the forearm extends straight forward.
There is a pair of muscles that bring the forearm closer to the arm; the larger one bends and curls the forearm with an inclination toward the inner side. For this single muscle originates from the lower prominence of the shoulder and from the head of the aforementioned coracoid process, inclining into the arm bone and terminating at the superior end of the bicipital tendon. The other muscle causes supination of the forearm, holding it with an inclination outward. For the origin of this muscle is on the back outer side of the arm bone. It is a muscle possessing two heads, one from the front and the other from the rear, both going to the humerus. Then they descend and join at the anterior lower end of the inferior bicipital tendon. The lower portion which pronates the forearm attaches to the upper aspect of the inferior bicipital tendon. Thus, they draw with strength. When these two muscles are drawn together, the forearm flexes forward in a straight manner. Within these two simple muscles is another muscle that encompasses the arm bone and flexes it. The pronator muscles of the forearm are a pair; they are on the outer side of the forearm. One originates from the lower end of the humerus and attaches to the upper ulna, forming a wrist joint. The other is shorter than the first, with wider fibers and nervous endings, originating from the lower portion of the ulna and attaching to the upper ulna at the wrist joint. The supinator muscles of the forearm are a pair; one is situated on the outer side of both elbows and attaches to the upper ulna without nerves. The origin of the second is from the outer upper side of the head of the arm bone, extending through the forearm and entering it. Thus, it proceeds until it approaches the wrist joint. It comes inward by the upper ulna and a membrane with a nerve terminates this muscle.
“[Praise be to] Allah, Whose glory is exalted, [for creating and operating all of this].”