Deltoid muscle

“ In paralysis of all the muscles surrounding a joint, when the limb is placid and no retractions by adapted atrophy have taken place, the artificial muscles can only serve to oppose the malpositions which are threatened from mechanical influences.
In the upper extremities prothetic apparatus has been principally used for progressive muscular atrophy. Paralysis of the wrist extensors is perhaps the only case in which the artificial muscle is required in anterior poliomyelitis. A string may be necessary to support the arm in paralysis of the deltoid, to avert luxation of the humerus. ”

“ Operation by two flaps, external and internal.—The outer—beginning nearly an inch below the acromion process, the hair in the axilla having been previously removed—is to be carried down with a gentle curve so deeply as to divide the deltoid muscle, and to show the long head of the triceps at its under and outer edge. The second incision is to be carried in a similar direction on the inside, through the deltoid muscle, but need not divide the insertion of the pectoralis major, which should be exposed. ”

“ When the whole of a broad muscle is united at a common point, as the deltoid which having many points of attachment above, is fixed below in a single tendon, the middle line of direction of all its fibres should be taken to estimate its uses. ”

“ And see, under the big deltoid, which fits round the shoulder like an epaulette and pulls the arm up, is the scapular group, things like tidily sorted skeins, thick on the shoulder-blades, diminished to a tendon string at their insertion in the arm; their business is to pull the arm back, in opposition to the big pectoral muscle which pulls it forwards. ”

“ The heart and the deltoid muscle are nearly equal in respect to their fleshy mass; now what would become of the circulation, if the first sometimes sent the blood with the force which the second uses to raise the superior extremity? A fit of anger, mania, &c. is sufficient to produce aneurisms. On the other hand the organic muscles are not affected with those prostrations of forces so common in the others; paralysis is foreign to them, because they are not within the cerebral influence. ”

“ As to the relations of the teres minor with the deltoid, they exist in man, seeing, in this case, the same muscle is, in its external portion, covered by this latter. With regard to the relations of the teres major with the posterior muscular mass of the arm, they also exist in man, since the external surface of this muscle is covered by the triceps. ”

“ Muscular action is one permanent cause of a new displacement. Suppose the humerus luxated downward, the pectoralis major, and the deltoid muscles draw its superior extremity upward and inward, which, offering to their action but a feeble resistance, changes its position and that in a two-fold direction.
27. The different motions of the arm may also, according to their direction, produce the same effect. Thus we have often witnessed a luxation inwards succeeding to a luxation downwards, in consequence of unskilful attempts to reduce it. ”

“ In woman it is generally less curved, smoother, and more slender than in man, and as bone is rough when the muscles attached are powerful, the right clavicle, being used more, is generally rougher and thicker than the left. Among the muscles attached are the large neck muscle, the sterno-cleido-mastoid, whose tendons form the presternal notch, the trapezius, the pectoralis major, and the deltoid. ”

“ The chest is supplied with numerous muscles which move the ribs up and down in the act of breathing. A great, fan-shaped muscle, called the pectoralis major, lies on the chest. It extends from the chest to the arm and helps draw the arm inward and forward. The arm is raised from the side by a large triangular muscle on the shoulder, the deltoid, so called from its resemblance to the Greek letter delta, Δ. The biceps, or two-headed muscle, forms a large part of the fleshy mass in front of the arm. ”

“ The extent of the origin of this muscle from the sternum, on which it leaves converging, parallel or diverging impressions, is of some taxonomic value.
Much labour has been bestowed by A. H. Garrod and Max Fürbringer upon the investigation of the variations of the inserting tendons of the patagial muscles (fig. 14) , mainly from a taxonomic point of view. The propatagialis longus muscle is composed of slips from the deltoid, pectoral, biceps and cucullaris muscles. Its strong belly originates near the shoulder joint from clavicle, coracoid and scapula. ”

“ After a fashion simple enough, but which it is necessary to describe, the clavicular fasciculi of the trapezius and the corresponding fasciculi of the sterno-cleido mastoid are united the one to the other; the portion of the deltoid which in man arises from the clavicle, by reason of the absence of this latter, is also combined with the fleshy mass formed by the preceding muscles. From this fusion results the muscle known as the mastoido-humeral. ”

“ If the paralysis be slight other muscles may escape. The characteristic form of lead paralysis consists in loss of power in the extensors of the hands and fingers, especially of the extensor communis, without implication of the supinator longus. The muscles affected are in the region of distribution of the musculo-spinal nerve. The deformity is known as wrist-drop. Next in order, the triceps and deltoid are most frequently attacked. The lower extremities commonly escape for a considerable time. When attacked, the extensor muscles of the feet and toes are the first to suffer. ”

“ Over this extremity are reflected the biceps and the brachialis muscles in a state of violent distension. These muscles, greatly irritated by such distension, continue in a state of habitual contraction, in consequence of which, they keep the fore-arm half-bent. Nor can the anconeus muscle, which is necessarily relaxed, act so as to prevent this semiflection. Severe pains would be the consequence of attempts to extend the fore-arm; the limb is in a state of pronation; yet I find among the cases collected by Desault, several examples where supination existed ”

“ The weight of the limb or a portion of it, by stretching paralyzed muscles, often aggravates their atrophy. This is most likely to occur with the paralyzed deltoid when the arm is unsupported, and with the anterior tibial muscles when the foot is allowed to drop.
Muscular atrophy occurs in the spinal paralysis of adults as well as in children; but in the latter alone does the atrophy extend to the bones and cartilages, tendons, fascia, ligaments, and blood-vessels. The osseous projections to which the muscles are attached waste ”

“ Its temporal attachment is to the groove, which is named from it, on the inner surface of the mastoid process: a large fleshy belly proceeds from this origin downward and forward, contracts to a round tendon, which usually pierces the stylo-hyoid muscle, traverses an aponeurotic ring lined by synovial membrane, which strongly binds it to the hyoid bone, near its lesser cornu, and is then reflected upward, expanding again to a strong muscular belly, which fixes itself by short aponeurotic fibres into the lower border of the jaw, at an oval depression beside the symphysis. ”

“ If those only are torn which connect the end of the bone to the acromion, there is mere rising of the end. But if—as is often the case when the violence has been great, as in a fall either from a height or with great velocity—the conoid and trapezoid ligaments connecting the tuberosity of the bone with the coracoid process, have given way, then the end of the bone projects, pushes out the deltoid, and gives rise to considerable flattening of the shoulder. ”

“ The extensor muscle of the wing does not pull on the power arm, but on the resistant arm on the other side of the fulcrum (c) . The illustration shows, however, how such a case is possible. The membrane of the joint fastening the wing-stalk to the thorax is turned up outwards below the stalk like a pouch. The tendon of the flexor of the wing passes through this pouch to its point of attachment (c) lying on the other side of the fulcrum (d) . Thus it is very simply explained how two muscles which act in the same direction can nevertheless have an entirely contrary working power. ”

“ Instead of being thus attached directly to the bone, they end in what we call tendons. These tendons are hard and strong, and a very small tendon will lift as much without breaking as quite a large muscle. The muscles are soft and would have to be attached over a large area in order to secure the required strength. The tendons, being so much stronger than the muscles, can be attached to a very small area and yet secure the same amount of power as would result from attaching the muscle itself.
The tendons pass directly into the periosteum, the thick, strong covering of the bones. ”

“ Other physical gymnastics seek to give strength to certain sets of muscles to the neglect of others. The rythmical movements of the Delsarte system bring into action each muscle of the body without wearying any, to the harmonious developing of all, since in all, save exceptional cases, it will be found, upon beginning this treatment, that more than half the muscles of the body are unused, while the other, and overworked half, move in stiff and angular fashion. ”

“ The theory underlying this name is that the muscles bend the arms ventrally, and the ligament by its elasticity restores them to their places; but there seems reason to believe that the "ligament" is really a dorsal muscle. It is particularly to be noted that similar muscles occur between the first and second radials, proving that the primary arm really begins with the first radial. The second and third radials, as also the first two ossicles and certain others of each arm, are closely united by calcified fibres, and this kind of union is called a "syzygy" (Fig. 265, syz) . ”

“ 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 ”

“ The simultaneous contraction of the two upper muscles causes the arm to bend upwards. The contraction of the two lower bend it downwards, whilst a sideward movement is effected by the contraction of the upper and lower muscle of the same side. On the proximal surface of the central portion of the vertebra there is a central knob and two ventro-lateral knobs, {482}a median ventral pit and two dorso-lateral pits, and on the distal surface there are pits corresponding to the knobs on the proximal side and vice versa (Fig. 210, C) . ”

“ 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 ”

“ 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. ”

“ 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. ”

“ 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) . ”

“ Many of the muscles are united to the bones by the direct contact of their fleshy fibers, but in other instances the body of the muscle is more or less gradually transformed into a cordy or membranous structure known as the tendon or sinew, and the attachment is made by the very short fibrous threads through the medium of a long tendinous band, which, passing from a single one to several others of the bones, effects its object at a point far distant from its original attachment. ”