A Treatise on Anatomy, Physiology, and Hygiene Part 9

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.

156. The interstices between the different muscles are filled with adipose matter, or fat. This is sometimes called the packing of the system. To the presence of this tissue, youth are indebted for the roundness and beauty of their limbs.

[Ill.u.s.tration: Fig. 37. A transverse section of the neck. The separate muscles, as they are arranged in layers, with their investing fasci, are beautifully represented. As the system is symmetrical, figures are placed only on one side. In the trunk the muscles are arranged in layers, surrounded by fasci, as in the neck. The same is true of the muscles of the upper and lower limbs.

12, The trachea, (windpipe.) 13, The oesophagus, (gullet.) 14, The carotid artery and jugular vein. 28, One of the bones of the spinal column. The figures that are placed in the white s.p.a.ces represent some of the fasci; the other figures indicate muscles.]

157. The muscles may be arranged, in conformity with the general division of the body, into four parts: 1st. Those of the _Head_ and _Neck_. 2d. Those of the _Trunk_. 3d. Those of the _Upper Extremities_. 4th. Those of the _Lower Extremities_.

156. Give a reason why the limbs of youth are rounder than those of the aged. Describe fig. 37.

[Ill.u.s.tration: Fig. 38. The superficial layer of muscles on the face and neck. 1, 1, The occipito-frontalis muscle. 2, The orbicularis palpebrarum. 6, The levator labii superioris 7, The levator anguli oris.

8, The zygomaticus minor. 9, The zygomaticus major 10, The ma.s.seter. 11, The depressor labii superioris. 13, The orbicularis oris. 15, The depressor anguli oris. 16, The depressor labii inferioris. 18, The sterno-hyoideus. 19, The platysma-myodes. 20, The superior belly of the omo-hyoideus. 21, The sterno-cleido mastoideus. 20, The scalenus medius.

23, The inferior belly of the omo-hyoideus. 24, The trapezius.[5]

_Practical Explanation._ The muscle 1, 1, elevates the eyebrows. The muscle 2 closes the eye. The muscle 6 elevates the upper lip. The muscles 7, 8, 9, elevate the angle of the mouth. The muscle 10 brings the teeth together when eating. The muscle 11 depresses the upper lip. The muscle 13 closes the mouth. The muscle 15 depresses the angle of the mouth. The muscle 16 draws down the lower lip. The muscles 18, 19, 20, 23, depress the lower jaw and larynx and elevate the sternum. The muscle 21, when both sides contract, draws the head forward, or elevates the sternum; when only one contracts, the face is turned one side toward the opposite shoulder. The muscles 18, 19, 20, 21, 22, 23, 24, aid in respiration.]

[5] In the plates ill.u.s.trating the muscular system, the names of such muscles are given as are referred to in the paragraph "Practical Explanation." These names need not be committed to memory. If a pupil wishes to acquire a knowledge of the general attachment of the muscles represented in the plates, he can do so by _comparing_ the muscular plate with that of the skeleton, (fig. 28.)

_Observation._ When we are sick, and cannot take food, the body is sustained by absorption of the fat. The removal of it into the blood causes the sunken cheek, hollow eye, and prominent appearance of the bones after a severe illness.

158. The number of muscles in the human body is more than five hundred; in general, they form about the skeleton two layers, and are distinguished into superficial and deep-seated muscles. Some of the muscles are voluntary in their motions, or act under the government of the will, as those which move the fingers, limbs, and trunk; while others are involuntary, or act under the impression of their proper stimulants, without the control of the individual, as the heart.

_Observations._ 1st. The abdominal muscles are expiratory, and the chief agents for expelling the residuum from the r.e.c.t.u.m, the bile from the gall bladder, the contents of the stomach and bowels when vomiting, and the mucus and irritating substances from the bronchial tubes, trachea, and nasal pa.s.sages by coughing and sneezing. To produce these effects they all act together. Their violent and continued action sometimes produces hernia, and, when spasmodic, may occasion ruptures of the different organs.

2d. The contraction and relaxation of the abdominal muscles and diaphragm stimulate the stomach, liver, and intestines to a healthy action, and are subservient to the digestive powers. If the contractility of their muscular fibres is destroyed or impaired, the tone of the digestive apparatus will be diminished, as in indigestion and costiveness. This is frequently attended by a displacement of those organs, as they generally gravitate towards the lower portion of the abdominal cavity, when the sustaining muscles lose their tone and become relaxed.

What causes the hollow eye and sunken cheek after a severe sickness?

158. How many muscles in the human system? Into how many layers are they arranged? What is a voluntary muscle? Give examples. What is an involuntary muscle? Mention examples. Give observation 1st, respecting the use of the abdominal muscles? Observation 2d.

[Ill.u.s.tration: Fig. 39. A front view of the muscles of the trunk. On the left side the superficial layer is seen; on the right, the deep layer. 1, The pectoralis major muscle. 2, The deltoid muscle. 6, The pectoralis minor muscle. 9, The coracoid process of the scapula. 11, The external intercostal muscle. 12, The external oblique muscle 13, Its aponeurosis.

16, The rectus muscle of the right side. 18, The internal oblique muscle.

_Practical Explanation._ The muscle 1 draws the arm by the side, and across the chest, and likewise draws the scapula forward. The muscle 2 elevates the arm. The muscle 6 elevates the ribs when the scapula is fixed, or draws the scapula forward and downward when the ribs are fixed.