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Biceps muscle relaxed. 1 and 3: Two heads of the muscle; 2: Muscular portion; 3: Tendon fastening to the fore-arm.

Biceps

Biceps muscle relaxed. 1 and 3: Two heads of the muscle; 2: Muscular portion; 3: Tendon fastening to…

Biceps muscle contracted to raise the fore-arm. 1 and 3: Two heads fastened at the shoulder; 2: Contracting portion; 4: End fastened to the fore-arm.

Biceps

Biceps muscle contracted to raise the fore-arm. 1 and 3: Two heads fastened at the shoulder; 2: Contracting…

A single fiber partly broken and greatly magnified. 1: The delicate fibrous cover unrboken; 2: The muscular substance within, separated.

Fibers

A single fiber partly broken and greatly magnified. 1: The delicate fibrous cover unrboken; 2: The muscular…

Fragments of striped (striated) muscle fibers, showing a cleavage in opposite directions, magnified 300 diameters. Striped muscle is nearly always under the control of the will, and is often spoken of as voluntary muscle. Labels: A, longitudinal cleavage; c, fibrillae separated from one another at the broken end of the fiber; c'c", single fibrils more highly magnified, in c; the elementary structures are square, in c" round; B, transverse cleavage; a, b, partially detached disks; b' detached disk, more highly magnified, showing the sarcous elements.

Fragments of Striped (Striated) Muscle Fibers

Fragments of striped (striated) muscle fibers, showing a cleavage in opposite directions, magnified…

Also known as unstriped muscle.

Plain Muscle

Also known as unstriped muscle.

Wave of contraction passing over a muscular fiber of dytiscus, very highly magnified. When a muscle contracts, the dark bands swell up and shorten (the light bands are also constricted), and the whole fiber broadens and shortens. Labels: R, R, portions of the fiber at rest; C, contracted part; I, I, intermediate condition.

Muscular Fiber Contracting

Wave of contraction passing over a muscular fiber of dytiscus, very highly magnified. When a muscle…