Part 9 (1/2)

146. What parts are injured in the displacement of a bone? 147. What causes the acute pain in sprains? What is a good remedy for this kind of injury? 148. What caution to persons of scrofulous const.i.tutions?

CHAPTER VIII

THE MUSCLES.

149. All the great motions of the body are caused by the movement of some of the bones which form the framework of the system; but these, independently of themselves, have not the power of motion, and only change their position through the action of other organs attached to them, which, by contracting, draw the bones after them. In some of the slight movements, as the winking of the eye, no bones are displaced.

These moving, contracting organs are the _Muscles_, (lean meat.)

ANATOMY OF THE MUSCLES.

150. The MUSCLES, by their size and number, const.i.tute the great bulk of the body, upon which they bestow form and symmetry. In the limbs, they are situated around the bones, which they invest and defend, while they form, to some of the joints, their princ.i.p.al protection. In the trunk, they are spread out to enclose cavities, and const.i.tute a defensive wall, capable of yielding to internal pressure, and rea.s.suming its original state.

151. In structure, a muscle is composed of _fas-cicu-li_ (bundles of fibres) of variable size. These are enclosed in a cellular membranous investment, or sheath. Every bundle composed of a number of small fibres, and each fibre consists of a number of filaments, each of which is enclosed in a delicate sheath. Toward the extremity of the organ the muscular fibre ceases, and the cellular structure becomes aggregated, and so modified as to const.i.tute _tendons_, (cords,) by which the muscle is tied to the surface of the bone. The union is so firm, that, under extreme violence, the bone will sooner break than permit the tendon to separate from its attachment. In some situations, there is an expansion of the tendon, in the manner of a membrane, called _Ap-o-neu-rosis_, or _Fasci-a_.

149. How are all the motions of the body produced? What are these motor organs called? 150-160. _Give the anatomy of the muscles._ 150.

What is said of the muscles? 151. Give their structure.

_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.

[Ill.u.s.tration: 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 a fan, converging to a tendinous point, and const.i.tuting a _radi-ate_ muscle. Again they are _penni-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-penni-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 a.s.signed 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 a.s.sists 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 are arranged in layers, one over another. The sheath of each muscle is loosely connected with another, by the cellular membrane.

153. What is meant by the origin of a muscle? The insertion? The swell? What is the color of muscles? With what is each muscular fibre supplied? 154. What is said of fascia? What is its appearance when freshly exposed? 155. What effect has it on the muscles? Give other uses of the fascia.