Observation. The pupil can examine a piece of boiled beef, or the leg of a fowl, and see the structure of the fibres and tendons of a muscle.
Fig. 36.
Fig. 36. 1, A representation of the direction and arrangement of the fibres in a fusiform, or spindle-shaped muscle. 2, In a radiated muscle. 3, In a penniform muscle. 4, In a bipenniform muscle. t, t, The tendons of a muscle.
152. Muscles present various modifications in the arrangement of their fibres, as relates to their tendinous structure. Sometimes they are completely longitudinal, and terminate, at each extremity, in a tendon, the entire muscle being spindle-shaped. In other situations, they are disposed like the rays of 66 a fan, converging to a tendinous point, and constituting a ra´di-ate muscle. Again they are pen´ni-form, converging, like the plumes of a pen, to one side of a tendon, which runs the whole length of the muscle; or they are bi-pen´ni-form, converging to both sides of the tendon.
How are tendons or cords formed? What is the expansion of a tendon called? How can the structure of muscles and their fibres be shown? What does fig. 36 represent? 152. Give the different arrangements of muscular fibres.
153. In the description of a muscle, its attachments are expressed by the terms “origin” and “insertion.” The term origin is generally applied to the more fixed or central attachment, or to the point toward which motion is directed; while insertion is assigned to the more movable point, or to that most distant from the centre. The middle, fleshy portion is called the “belly,” or “swell.” The color of a muscle is red in warm-blooded fish and animals; and each fibre is supplied with arteries, veins, lymphatics, and both sensitive and motor nervous filaments.
154. The FASCIA is of various extent and thickness, distributed through the different regions of the body, for the purpose of investing and protecting the softer and more delicate organs. An instance is seen in the membrane which envelopes a leg of beef, and which is observed on the edges of the slices when it is cut for broiling. When freshly exposed, it is brilliant in appearance, tough, and inelastic. In the limbs it forms distinct sheaths to all the muscles.
155. This tendinous membrane assists the muscles in their action, by keeping up a tonic pressure on their surface. It aids materially in the circulation of the fluids, in opposition to the laws of gravity. In the palm of the hand and sole of the foot, it is a powerful protection to the structures that enter into the formation of these parts. In all parts of the system, the separate muscles are not only invested by fascia, but they 67 are arranged in layers, one over another. The sheath of each muscle is loosely connected with another, by the cellular membrane.