İKİNCİ FEN · ÜÇÜNCÜ BÂB · İKİNCİ FASIL · Beşinci Madde
Article Fifth
Concerning the muscles and movements of the fingers.
O, esteemed one! Know that anatomists have said: Some of the muscles which move the fingers of the hand are located within the palm's bones. Others are attached to the forearm bones. Were they all in the palm, the flesh would be too abundant, rendering it heavy and lacking grace. The hand would not possess this refinement; for the wrist muscles would remain distant from the fingers. Therefore, it is circular, strong, and lengthened, strengthened by membranes from every direction. Its fibers are wide and encompassing, created so that they may attach to movable organs.
All the muscles which move and extend the fingers downwards are situated upon the forearm bone. Thus, a muscle that moves the fingers downward, extending them, resides in the middle of the back side of the forearm bone, originating from its lower head externally, sending fibers to the four fingers, moving them downward and spreading them open. Three of these opening muscles are adjacent to one another on one side; one is part of the flexor, arising from the middle portion between the two prominences of the forearm’s external head, sending two fibers to the little finger and ring finger. The second of these layered muscles is part of the flexor, originating beneath the two prominences of the forearm bone and alongside the lower arm bone, sending two fibers with its center to the middle and index fingers. The third originates from the upper side of the upper arm bone [126/a], sending a fiber to the thumb. There is another muscle beside this one, which has been explained in the section on wrist muscles. Its origin is the middle of the upper arm bone; its fiber keeps the middle and index fingers distant from the thumb.
Some of the muscles that attach and grasp the fingers are located upon the forearm bone, while others reside within the palm.
There are three muscles upon the forearm bone, arranged in succession one above another in its middle. The most valuable among them is the one found lowest, attached to the bone of the lower end. Its function being so important, its place is kept secure. These lower muscles originate from the inner side of the external prominence at the lower end of the forearm bone, their fibers wide, and when they divide into five tendons, each tendon goes to a finger, causing flexion (contraction) in the first, second, and third joints of the four fingers. The thumb’s fiber causes flexion in its second and third joints. The second muscle is above this one and smaller, originating from the head of the forearm bone, providing slight attachment to the lower end. It passes over the upper surface of the upper end, which is the common boundary between the outer and inner sides, reaching towards the thumb side, then turns inward, sending its fiber to the joints of the four fingers, so that they may be held.
The third muscle is not for grasping; rather, its fiber enters into the palm and expands within the palm, becoming wide and encompassing. Thus, it gives a sense of touch to the palm, prevents hair from growing in the palm, and grants strength and firmness to the hand in acts of taking and giving.
“No one has power to change events except God Most High.”