Fig. 46. An anterior view of the muscles of the body. 1, The frontal swell of the occipito-frontalis. 2, The orbicularis palpebrarum. 3, The levator labii superioris. 4, The zygomaticus major. 5, The zygomaticus minor. 6, The masseter. 7, The orbicularis oris. 8, The depressor labii inferioris. 9. The platysina myodes. 10, The deltoid. 11, The pectoralis major. 12, The latissimus dorsi. 14, The biceps flexor cubiti. 15, The triceps extensor cubiti. 16, The supinator radii longus. 18, The flexor carpi radialis longior. 19, The flexor cominunis digitorum. 20, The annular ligament. 21, The palmar fascia. 22, The obliquus externus abdominis. 25, The psoas magnus. 27, The adductor longus. 28, The sartorius. 29, The rectus femoris. 30, The vastus externus. 31, The vastus internus. 32, The tendon patellæ. 33, The gastrocnemius. 34, The tibialis anticus. 36, The tendons of the extensor digitorum communis.

Fig. 47. A posterior view of the muscles of the body. 3, The complexus. 4, The splenius. 5, The masseter. 6, The sternocleido mastoideus. 7, The trapezius. 8, The deltoid. 10, The triceps extensor. 13, The tendinous portion of the triceps. 14, The anterior edge of the triceps. 15, The supinator radii longus. 17, The extensor communis digitorumn. 18, The extensor ossis metacarpi pollicis. 19, The tendons of the extensor communis digitorum. 20, The olecranon process of the ulna and insertion of the triceps. 21, The extensor carpi ulnaris. 22, The extensor communis digitorum. 24, The latissimus dorsi. obliquus externus. 27, The gluteus medius. biceps flexor cruris. 30, The semi-tendinosus. tendo Achillis.

25, Its tendinous origin.
28, The gluteus magnus.
31, 32, The gastrocnemius.

26, The 29, The 33, The

Practical Explanation. The muscle 1, fig. 46, by its contraction, raises the eyebrows. The muscle 2, fig. 43, closes the eyelids. The muscle 3, fig. 46, elevates the upper lip. The muscles 4, 5, fig. 48, elevate the angles of the mouth. The muscles 6, fig. 46, and 5, fig. 47, bring the teeth together. The muscle 7, fig. 46, closes the mouth. The muscle 8, fig. 46, depresses the lower lip. The muscles 9, fig. 46, and 6, fig. 47, bend the neck forward. The muscles 3, 4, fig. 47, elevate the head and chin. The muscle 22, fig. 45, bends the body forward, and draws the ribs downward. The muscle 11, fig. 48, brings the shoulder forward. The muscle 7, tig. 47, draws the shoulder back. The muscles 10, fig. 46, and 8, fig. 47, elevate the arm. The muscles 11, fig. 46, and 24, fig. 47, bring the arm to the side. The musele 14, fig. 46, bends the arm at the elbow. The muscle 10, fig. 47, extends the arm at the elbow. The muscles 16, 18, fig. 46, bend the wrist and fingers. The muscl 19 bends the fingers The muscles 18, 21, 23, fig. 47, extend the wrist. The muscle 23, fig. 47, extends the fingers. The muscles 26, 27, 28, fig. 46, bend the lower limbs on the body, at the hip. The muscle 28, fig. 46, draws one leg over the other, (the position of a tailor when sewing.) The muscles 27, 28, fig. 47, extend the lower limbs on the body, at the hip. The muscles 29, 30, 31, fig. 46, extend the leg at the knee. The muscles 29, 30, fig. 17, bend the leg at the knee. The muscles 34, 36, fig. 46, bend the foot at the ankle, and extend the toes. The muscles 31, 32, 33, fig. 47, extend the foot at the ankle.

Note. Let the anatomy and physiology of the muscular system be reviewed, in form of topics, from figs 16, 47, or from the anatomical outline plates No. 3 and 4.

CHAPTER X.

HYGIENE OF THE MUSCLES

173. The muscles should be used, in order that the size and strength of these organs may be adequate to the demand made upon them. It is a law of the system that the action and power of an organ are commensurate, to a certain extent, with the demand made upon it; and it is a law of the muscular system that, whenever a muscle is called into frequent use, its fibres increase in thickness within certain limits, and become capable of acting with greater force; while, on the contrary, the muscle that is little used decreases in size and power.

Illustrations. 1st. The blacksmith uses and rests the muscles of his arm when striking upon the anvil. They not only incrcase in size, but become very firm and hard.

2d. The student uses the muscles of the arm but little, in holding his books and pen; they not only become small,

but soft.

3d. Let the student leave his books, and wield an iron sledge, and the muscles of his arm will increase in size and firmness. On the other hand, let the blacksmith assume the student's vocation, and the muscles of his arm will become soft and less firm.

174. When the muscles are called into action, the flow of blood in the arteries and veins is increased. The increased flow of blood in the arteries and veins, causes a more rapid deposition of the particles of matter of which the muscles are

173-211. Give the hygiene of the muscles. 173. What is necessary that muscles may attain size and strength? Give a law of the muscular system. Show this by practical illustrations. 174. Why do muscles increase in size when exercised?

composed. If the exercise is adequate to the power of the system, the deposit of new material will exceed in quantity the particles of matter removed, and both the size and energy of the muscles are increased. But there is a limit to the muscles becoming strong by labor. Sooner or later, man will attain his growth or power; yet by judicious exercise, care, and discreet management, the greatest power of the muscles may be preserved until advanced age.

175. The muscles are lessened in size and diminished in power when the exercise is continued so as to produce a feeling of exhaustion. The loss of material, in this instance, will exceed the deposition of the atoms of matter. This is seen in the attenuated frames of over-tasked domestic animals, as the horse. The same truth is illustrated by the laborious agriculturist, who, in consequence of too severe toil while gathering the products of the field, frequently diminishes his weight several pounds in a few weeks. Exercise, either for pleasure or profit, may fatigue, yet it should never be protracted to languor or exhaustion, if the individual desires " green old age."

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176. The same amount of exercise will not conduce to the health of all individuals. If riding or walking one mile causes slight fatigue, this may be beneficial; while, by travelling two miles, the exhaustion may be highly injurious. Exercise and labor should be adapted to the strength of particular individuals. How little soever the strength, that must be the measure of exertion. Any other rule would be fatal to the hopes of invigorating the system, either by exercise or labor.

Is there a limit to the muscles becoming powerful by action? How may the strength of muscles be kept until advanced age? 175. What is the effect when exercise is continued until there is a feeling of exhaustion! Give a practical illustration. What rule is mentioned in regard to exercise? 176. Can all persons take the same amount of exercise? What rule is given as to the amount of exercise?

177. Relaxation must follow contraction, or, in other words, rest must follow exercise. The necessity of relaxation, when a muscle has been called into action, is seen in the example of a boy extending his arm with a book in his hand, as a penalty. The boy can keep the arm extended but a short time, make what effort he may. It is also seen in the restlessness and feverish excitement that are evinced by persons gazing on troops during days of review. The same is noted in shopping. Such employments call into action the muscles that support the spinal column in an erect position, and the languor or uneasiness is muscular pain. The longcontinued tension of a muscle enfeebles its action, and event. ually destroys its contractility.

178. In school, the small children, after sitting a short time, become restless. If their position be changed, their imperfectly developed muscles will acquire tone, and will again support the spinal column erect without pain. The necessity for frequent recesses in school, is founded on the organic law of muscular action alternating with rest. The younger and feebler pupils are, the greater the necessity for frequent recesses. We would not have the teacher think that one half of the time should be spent in recesses; or the mother, that her daughter is going to school to play. But we do maintain that recesses should be given, and that they should be short and frequent, especially for small and feeble scholars.

179. Exhaustion is the inevitable result of continued muscular contraction. For example, let a lady ply the needle quickly for some hours, and the muscles of the back and right arm will become exhausted, which will be indicated by a sense of weariness in these parts. A change of employ

177. What is said of the contraction and relaxation of the muscles? Give examples of the necessity of relaxing the muscles. 178. Why should not small children be confined in one position for a long time? What evils result from this practice? What class of pupils should have recesses most frequently 179. What effect has continued muscular contraction?