Intercostal muscle

“ Part II commences with a memoir by Professor Martin and Edward M. Hartwell, on the respiratory function of the internal intercostal muscles. The authors show how conflicting are the opinions regarding the particular mechanical work done by these muscles; and how impracticable it is to decide by a simple mechanical study as to whether these muscles are rib-elevators or rib-depressors. Dogs and cats were used in their experiments, which show that the muscles in question are expiratory in their function throughout their whole extent. ”

“ For the Diaphragme being made useless by loosing its Nerves, the Intercostal Muscles do dilate the Ribs much more than formerly, even to the utmost distance they can, when there is need for it; as, when you make the Dog run a little after he is cut, or when you gallop a Wind-broken Horse, doth manifestly appear. ”

“ The gap in the muscle becomes filled with blood, and this in time is replaced by connective tissue, which forms a bond of union between the ends. When the space is considerable the connecting medium consists of fibrous tissue, but when the ends are in contact it contains a number of newly formed muscle fibres. In the process of repair, one or both ends of the muscle or tendon may become fixed by adhesions to adjacent structures, and if the distal portion of a muscle is deprived of its nerve supply it may undergo degeneration and so have its function impaired. ”

“ Perfect freedom of movement is insured by the bones being covered with glistening cartilages, and a delicate and moist membrane, and the motion from the shape of the apparatus is almost equal to that of a chandelier where there is what is called a cup-and-ball joint at the ceiling. It has already been noticed that muscles are attached to the blade-bone and to the arm-bone below the joint, and that, this being movable, when they contract they move the arm, and the instance was given of the action of the deltoid muscle in raising the arm. ”

“ Once the joint is flexed, the involuntary contraction of the flexor muscles maintains the attitude, and if the patient is able to use the limb in walking, the weight of the body is a powerful factor in increasing it. The eversion of the leg is probably associated with contraction of the biceps muscle. Backward displacement of the tibia is met with chiefly in neglected cases of chronic disease of the knee when the child has walked on the limb after it has become flexed. ”

“ Furthermore, they have no striations, and their connection with the nerve fibers is less marked. They are also much smaller than the striated cells, being less than one one-hundredth of an inch in length and one three-thousandth of an inch in diameter.
In the formation of the non-striated muscles, the cells are attached to one another by a kind of muscle cement to form thin sheets or slender bundles. These differ from the striated muscles in several particulars. They are of a pale, whitish color, and they have no tendons. ”

“ Here, alone, at the distal portion of the tendon, occur muscular fibres, but these are unstriped, belonging to the category of cutaneous muscles. We have here the interesting fact that a muscle (portion of the triceps humeri of the reptiles) has been reduced to a tendon, which in a secondary way has become connected with cutaneous muscles, which, when strongly developed, represent its belly. ”

“ There are but few motions in the economy that are simple, but few muscles that can contract separately. Almost every sort of contraction supposes another, and for this reason; the two points to which a muscle is ordinarily attached are both capable of being moved; if one of them was not fixed, both would then be put in motion when the muscle contracted; thus in the contraction of its extensors, the leg if it was not fixed would approach the foot as much as the foot approached the leg ”

“ In the upper part of the leg the tibialis anticus, A, Plate 67, Figure 2, and extensor-communis muscle, B, are adherent to the fascia which covers them, and to the intermuscular septum which divides them. In the lower part of the leg where these muscles and the extensor pollicis, C, terminate in tendons, a b c, they are readily separable from one another. The tibialis anticus lies along the outer side of the tibia, from which, and from the head of the fibula and interosseous ligament, it arises tendinous and fleshy. This muscle is superficial in its whole length ”

“ In one leg, a small accessory bundle of fleshy fibers arises from the proximal end of the first metatarsal (widely separated from the origin of the distal head) , passes through the retinaculum deep to the common tendon and attaches to the dorsal surface of the articular capsule of the metatarsophalangeal joint; thus this bundle is completely separate from the remainder of the muscle. In two legs, the same nerve branch that gives twigs into the proximal head also gives off (much farther distally) a twig that enters the distal head. ”

“ In the more posterior intercostal spaces these muscles are poorly developed, but they become progressively better developed anteriorly, and are fully represented in the most anterior intercostal spaces. ”

“ Fig. 53 represents the muscles of the arm after the skin and flesh are removed. They are all in smooth silky cases, laid over each other, and separated both by the smooth membranes that encase them and by layers of fat, so as to move easily without interfering with each other. They are fastened to the bones by strong tendons and cartilages; and around the wrist, in the drawing, is shown a band of cartilage to confine them in place. The muscle marked 8 is the extensor that straightens the fingers after they have been closed by a flexor the other side of the arm. ”

“ Some fibers arise from the distal [Pg 437] edge of the tendon of insertion of M. extensor iliofibularis. Medial head: This arises fleshily from the posterior surface of the tibiotarsus just medial to the distal part of the posterior head, distal to M. popliteus, and either lateral or distolateral to the origin of M. plantaris. Distal to the junction of the three heads, the muscle arises fleshily from the posterior surface of the tibiotarsus (except the distal part) and from the medial and posterior surfaces of the fibula. ”

“ They are attached chiefly to bones but also to cartilages, ligaments, and skin, either by means of tendons, which are cords or bands of white inelastic fibrous tissue, or by means of aponeuroses, membranous expansions of the same nature. Most voluntary muscles consist of a belly and two ends or tendons. The origin is the fixed point from which it acts while the movable point upon which it acts is known as its insertion.
Action of the Muscles.—When attached to bones, muscles are distributed in three ways: 1. When it is necessary to produce much motion rapidly, a short muscle is used. ”

“ As osseous union of the fragments is not essential to a good functional result, and as fibrous union does not necessarily entail any material interference with the usefulness of the limb, no attempt need be made to approximate the fragments, but every effort must be made to maintain the function of the quadriceps muscle and the mobility of the joint. ”

“ Between two muscles thus opposed, there is often no solid intermediate organs, as in the lips, the linea alba, &c. The muscle of one side acts then directly upon that which corresponds to it, in order to distend it. Now this action of the muscles upon each other is precisely the phenomenon of the antagonists; two muscles are such when one cannot contract without elongating the other and vice versa. Let us examine in this phenomenon the part of the contractility of texture ”

“ We do not have, then, in these organs the fine subdivision of control that there is in the skeletal muscles, for a single skeletal motor cell in the spinal cord connects with one or, at the most, a very few muscle fibers. If we consider the uses to which smooth muscles are put, we shall see that finely subdivided control is not important, as it is in the case of the skeletal muscles, where the movements have to be graded very accurately. Smooth muscles are present in the stomach and intestines and other abdominal organs which make movements. ”

“ When the nerve discharges its influence into the muscles, a very rapid molecular change takes place in the substance contained in the cartouches or muscular boxes, which contract, pressing their ends close together. Scarcely has the action of the nerves ceased than they relax and resume their previous form. It is well known, that when a muscle contracts, it becomes thicker and shorter; it suffices to take hold of the arm a little above the elbow and then to bend it in order to feel how the biceps muscle swells and hardens. ”

“ The muscle is well supplied with blood, and the nerve which endows it with energy is particularly well prevented from being compressed during the movements of the muscles amongst which it runs, any compression being very injurious. The upper edge of the blade-bone is notched, and a dense tissue or ligament stretches from one point of the notch to the opposite one, enclosing a small open space; now the nerve runs through this space, and is protected by the hard tissues of bone and ligament from the contraction of the soft muscles. ”

“ It is only by reason of the homology of situation with the corresponding muscle in man that we give the name under which we are studying it; indeed, its structure is different, for it does not present the long, broad, aponeurotic tendon which, in its superior part, characterizes this muscle in the human species.
It arises above from the inferior surface of the ischium, and from the tuberosity of the same bone. In the pig, and especially in the horse, it passes further upwards, to arise from the aponeurosis of the coccygeal muscles. ”

“ The first branch, sometimes large, sometimes small, passes to the lymphatic gland in the hollow of the shoulder, and to the adjacent muscles; it supplies the clavotrapezius, acromiotrapezius, levator scapulæ ventralis, splenius, occipitoscapularis, and rhomboideus. A second branch passes between the subscapularis and supraspinatus muscles, dividing into various branches which supply the muscles named. The third branch pierces the supraspinatus muscle, just craniad of the acromion process, and ramifies in that muscle. ”

“ Observe that but few of the muscles in the economy are found between two levers so great, consequently are capable of being so much distended, and especially of being so with a force greater than that of their contraction; for every muscular rupture supposes the excess of the external motion, which distends, over that of the fleshy fibres which contract to oppose this distension. If the external efforts were concentrated upon a single muscle, they would be able more often to overcome the resistance ”

“ It remains to be determined how many specimens need to be studied in order to obtain a fairly accurate picture of variation.
Comparison with Other Studies of Innervation
I accept the following concept of muscle-nerve relationship. All muscles of the pelvic limb of birds have developed phylogenetically [Pg 453] from either the dorsal extensor muscle mass or the ventral flexor muscle mass. The former was (at least originally) supplied by only the femoral and peroneal nerves ("dorsal" nerves) , the latter by only the obturator and tibial nerves ("ventral" nerves) . ”

“ It extends the forearm on the arm. Further, it makes tense the aponeurosis into which it is inserted; this explains the name of tensor of the fascia of the forearm, which is sometimes given to it.
It seems to us interesting to add that, abnormally, we sometimes find in man an analogue of this muscle. It is given off from the latissimus dorsi, near the insertion of the latter into the humerus; it accompanies the long head of the triceps and becomes fused with it. Sometimes it is inserted into the olecranon process, at other times into the antibrachial aponeurosis or the epitrochlea. ”

“ When these forces cease to be in action, immediately the contractility of texture of the elongated muscle, which had a tendency to exert itself, but was prevented, exerts itself, becomes efficacious, and draws back the moveable part to the middle position, a position in which the equilibrium is restored. Hence why in all the cases in which the cerebral influence has no power over the muscles, in which they are not irritated by stimulants, the limbs are uniformly found in a medium position between extension and flexion, abduction and adduction, &c. ”

“ In the muscles of animal life, when the contraction ceases, the muscle does not in general go back itself to the state it was in antecedent to the contraction, but it is drawn back to it by its antagonist; for example, when the biceps is contracted to bend the fore-arm and its contraction ceases, it becomes passive ”

“ The muscle is enlarged in such a manner that a lateral expansion of its mass is apparent in superficial or dorsal view (compare figures 15 and 16) . This, of course, indicates a muscle with powerful contraction, which has been unable to enlarge its circumference symmetrically because the eye is immediately dorsal to the muscle. Therefore it has expanded laterally. Ventral expansion is blocked by the presence of other muscles, and medially there is no surface for the insertion of additional fibers on the orbital process of the quadrate. ”