Muscular system

“ The muscular system is highly symmetrical and simple: along all eleven segments, there is a narrow, medial, ventral and dorsal clear space; on both sides of which space there is a band of longitudinal muscles, which, though encroaching on the two sides, and rather largely on the dorso-lateral sides, may be called the ventral and dorsal muscles. ”

“ Muscular system of the feet.—This consists of the retractors of the feet connected with the outer transverse muscle and the circular layer of muscles. In addition to these muscles there are intrinsic transverse muscles which cross the cavity of the feet in various directions (Pl. 51, fig. 20) . There is no special circular layer of fibres.
Histology of the muscle.—The main muscles of the body are unstriated and divided into fibres, each invested by a delicate membrane. Between the membrane and muscle are scattered nuclei, which are never found inside the muscle fibres. ”

“ Both evidently derive the principle of the activity that marks them from the same external and internal media; but, while the muscle, a mechanical organ, is limited to the obedient transformation of the force assigned to it, under the form of heat, into a measurable amount of work, the nerve, a vital organ, remains impenetrable and inaccessible to our calculations, and exerts its characteristic and sovereign powers in its own way, through a series of operations that escape all estimates of their force and heat. On the part of the muscular system, every thing can be measured ”

“ The muscular system requires further investigation, not so much the different systems of the striated voluntary musculature—for these have been for the most part compared in the two groups of animals in previous chapters—as the involuntary unstriped musculature, about which no word has been said. ”

“ After general growth is finished in length, our organs then increase in thickness; and it is especially in the muscles that this phenomenon is remarkable. To the slender and delicate body and round forms of the youth and young man, succeeds a large, strong and thick body with well developed forms. The muscles can be traced414 through the integuments, eminences and depressions are observed in them; different depressed lines serve as limits to various prominent ones. The animal muscular system is then more prominent in a state of repose, than it is in youth in its greatest motions. ”

“ Now every organ in the body is either in itself a muscle or a system of muscles, or is controlled by muscles. That is to say, none of the infinite processes incidental not only to any movement, but to even perfectly passive life, are independent of muscular action, automatic it may be, and unconscious or sub-conscious, but still muscular.
The action of the heart itself, for instance, which is, in ordinary circumstances, entirely automatic and absolutely essential to life, consists in the alternate contraction and expansion of muscle, which sends the blood to all parts of the body ”

“ To show the Structure of a Joint.—Procure from a butcher the joint of some small animal (hog or sheep) . Cut it open and locate the cartilage, synovial membrane, and ligaments. Observe the shape and surface of the rubbing parts and the strength of the ligaments.
[pg 243] CHAPTER XV - THE MUSCULAR SYSTEM As already stated, the skeleton, the nervous system, and the muscular system are concerned in the production of motion. The skeleton and the nervous system, however, serve other purposes in the body, while the muscular system is devoted exclusively to the production of motion. ”

“ Here, then, we have another beautiful illustration of the wisdom and beneficence of the Creator in so ordering that those muscles which are essential to the continuation of life shall perform their functions without the control or attention of the individual.
The study of the muscular system involves an exposition of the principles by which exercise should be regulated, and can scarcely fail to excite the attention of the general reader, and especially of those who, as parents or teachers, are interested in the education of the young. ”

“ It necessitates careful diet and constant exercise for a long period, and proves equally beneficial to both sexes. This book has been written in vain if the reader has not grasped by now that the activity of the muscles implies the activity of all the organs in the body. Accordingly, the whole muscular system is by appropriate methods given frequent exercise: gentle at first; never exhausting; but constantly increasing as the strength grows. The result is a general development of the organs throughout the body, which will in time work a complete metamorphosis in the individual’s physique. ”

“ IX. Finally, experiments upon the human subject show that the direct source of muscular power is to be looked for in the muscular system itself. The exercise of muscular power immediately involves the destruction of a certain amount of muscular substance, of which the nitrogen excreted is a measure. Indirectly, nitrogenized food is a source of power, as, by its assimilation by the muscular tissue, it repairs the waste and develops the capacity for work ”

“ The muscular differences noted in individuals are in reality the difference in the nerve cells, the action of the muscle indicating the activity of the central nervous system. When the muscles are being exercised the nerve cells are being exercised, and the effect of exercise on the nerve cells indirectly determines the muscular activity. ”

“ The muscles are like the various bits of machinery which go to make up a steam engine. In performing their work they produce heat and motion. The fuel which supplies this force is taken into the body as food, prepared for use in the intestinal tract, and from there carried by the blood to be stored up in the muscles and various tissues as latent force. Through the circulation of the blood the whole body is heated by muscular exercise. It stands to reason that continual exercise of a certain kind will develop certain muscles. ”

“ From these facts, as well as from the great force with which the muscle contracts, one must conclude that the muscle is a transformer of energy—that within its protoplasm, chemical changes take place whereby the potential energy of oxygen and food is converted into the kinetic energy of motion.
Fig. 113—Capillaries of muscles. Plan of Using Muscular Force.—Two difficulties have to be overcome in the using of muscular force in the body. The first of these is due to the fact that the muscles exert their force only when they contract. They can pull but not push. ”

“ There are three kinds of muscle cells in our bodies. The simplest are those that are found in the wall of the stomach and intestines and other internal organs that are capable of movements; the next kind is found only in the heart; the third, and most complex, makes up the bulk of our muscular tissue; it is the muscle that moves the bones. The first kind, because it shows no particular markings when examined through the microscope, is usually called smooth muscle ”

“ Structure of Voluntary Muscles. The main substance which clothes the bony framework of the body, and which forms about two-fifths of its weight, is the voluntary muscular tissue. These muscles do not cover and surround the bones in continuous sheets, but consist of separate bundles of flesh, varying in size and length, many of which are capable of independent movement.
Each muscle has its own set of blood-vessels, lymphatics, and nerves. It is the blood that gives the red color to the flesh. ”

“ Most of the bodily movements, such as affect the limbs and the body as a whole, are performed by muscles under our control. These muscles make up the red flesh or lean parts, which, together with the fat, clothe the bony framework, and give to it general form and proportion. We call these muscular tissues voluntary muscles, because they usually act under the control of the will.
The internal organs, as those of digestion, secretion, circulation, and respiration, perform their functions by means of muscular activity of another kind, that is, by that of muscles not under our control. ”

“ Of course this possibility of variation is of great advantage in our use of our muscles. It depends upon the very large number of individual fibers of which even our smallest muscles are made up. Whenever any single fiber contracts, it pulls to its full extent; if only a few become active, the pull of the whole muscle will be slight; as more come into action, more force will be exerted; the muscle will show its utmost power when all the fibers are contracting at once. We are conscious of greater mental effort when we make a powerful muscular contraction. ”

“ Fig. 112—Muscle cells from the heart, highly magnified (after Schäfer) . The Muscular Stimulus.—The inactive, or resting, condition of a muscle is that of relaxation. It does work through contracting. It becomes active, or contracts, only when it is being acted upon by some force outside of itself, and it relaxes again when this force is withdrawn. Any kind of force which, by acting on muscles, causes them to contract, is called a muscular stimulus. Electricity, chemicals of different kinds, and mechanical force may be so applied to the muscles as to cause them to contract. ”

“ We may class muscles as striated or voluntary and unstriated or involuntary. A third class, mixed, is represented by the heart muscle. The striated is represented by the skeletal muscles, and the unstriated by the thin muscular layers that form part of the wall of the stomach, intestines, bladder and other hollow organs. ”

“ These cases are generally accompanied by round shoulders and flat chest, protrusion of the abdomen, and rotation of the vertebræ.
A muscle can be developed only by the active contraction and relaxation of its fibers. Continuous tension quickly tires and lowers its tone, so that exercises given for increasing muscular power should be comparatively quick and frequently repeated, while those that aim at the stretching of muscles and ligaments should be slow and long maintained. ”

“ Every muscle, in fact, consists in the first place of a mass of muscular substance. This muscular substance is made up of an immense number of soft strings or fibres, all running in one direction and done up into large and small bundles. At either end of the muscle these soft muscular fibres are joined on to firmer but thinner fibres of connective or fibrous{29} tissue. And these thinner but firmer fibres make up the cord or band of tendon with which the muscle finishes off at either end. ”

“ The unstriped muscle is very simple, consisting merely of long spindle-shaped cells, but the striped or voluntary muscle is of more complex construction. Every voluntary muscle consists of myriads of tiny fibres, bound together in little bundles, enveloped in a kind of sheath. Fig. 24 is an example of this muscular fibre, taken from beef. When soaked in spirit, it often splits into a number of discs, the edges of which are marked by the transverse lines. ”

“ It is difficult for the youth to hold his back straight and his shoulders back; he is awkward and ungainly in his movements and becomes easily fatigued because of the condition of his muscles. [31] But the muscles follow immediately in their development and rapidly gain volume and tonicity, filling out the arms, legs, back and shoulders with large masses of firm muscular tissue. The growth of these muscle masses changes the dimensions of the youth and he fills out in his girths as rapidly as, in the previous period, he increased in length measurements. ”

“ All manner of movements are produced by muscles pulling sometimes with and sometimes against each other. But you will find when you come to examine them that all the movements of which your body is capable depend at bottom on this—that certain muscular fibres, in obedience to a something reaching them through their nerves, contract, shorten, and grow thick, and so pull their one end towards the other, and that to do this they must be continually supplied with pure blood. ”

“ Further, inasmuch as muscular movement is one of the chief ends, or the most important means to the chief ends of animal life, we find the animal body abounding in motor mechanisms, in which the prime mover is muscular contraction, while the machinery is supplied by complicated arrangements of muscles with such indifferent tissues as bone, cartilage, and tendon. ”

“ We must try to discover, for instance, what there is in common between the muscle in repose and the muscle in contraction, and to perceive in the muscular tonus a kind of bridge thrown between these two conditions. The functional activity would be uninterrupted, but it would have its degrees of activity. The muscular tonus would be the permanent condition of an activity which is capable only of being considerably raised or lowered. ”

“ The muscular tissues constitute and carry out the power, force, or energy of the body. They set the body in motion. They do the work. They regulate the delicate movements of the organs of special sense or function, as the eye, the ear, the tongue, the nose, larynx, thorax, abdomen; and fighting, defending, building, destroying, labor and mechanical skill of whatever nature, depend on them. Of exercise, sport, pain and pleasure, sensation, emotion, expression of the face, in fact all in all in every act of life, the muscles, the voluntary muscles, must perform the work. ”

“ The well-trained muscles contain only healthy protoplasm, and give off but a small percentage of nitrogenous decomposition products. Let the well-fed person who takes but little exercise, run half a mile, or play a simple game of ball, and the following day the muscles will be stiff and sore; this unusual exertion has caused the breaking down of much loosely organized tissue which could have been made firm and healthy by daily muscular activity. ”