Book - Buchanan's Manual of Anatomy including Embryology 9

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I have decided to take early retirement in September 2020. During the many years online I have received wonderful feedback from many readers, researchers and students interested in human embryology. I especially thank my research collaborators and contributors to the site. The good news is Embryology will remain online and I will continue my association with UNSW Australia. I look forward to updating and including the many exciting new discoveries in Embryology!

Frazer JE. Buchanan's Manual of Anatomy, including Embryology. (1937) 6th Edition. Bailliere, Tindall And Cox, London.

Buchanan's Manual of Anatomy: I. Terminology and Relative Positions | II. General Embryology | III. Osteology | IV. Bones of Trunk | V. Bones of Head | VI. Bones of Upper Limb | VII. Bones of Lower Limb | VIII. Joints | IX. The Upper Limb | X. Lower Limb | XI. The Abdomen | XII. The Thorax | XIII. Development of Vascular Systems | XIV. The Head and Neck | XV. The Nervous System | XVI. The Eye | XVII. The Ear | Glossary
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Chapter IX The Upper Limb

The Back

Landmarks. — The middle line of the neck presents a median furrow, called the nuchal groove, the presence of which is due to the shortness of most of the cervical spinous processes and the prominence on either side of the muscle masses at the back of the neck. At the upper end of this groove the strong bifid spine of the axis may be felt on deep pressure with the finger, but the spines of the third, fourth, and fifth cervical vertebrae cannot be detected, as these, falling short of the surface, permit dorsal flexion of the neck. At the lower end of the groove the spine of the seventh cervical or vertebra prominens is a wellmarked and easily recognized prominence; above it the spine of the sixth cervical can usually be detected on deep pressure; below it the spines of all the thoracic and lumbar vertebrae can be recognized, especially if the back is bent forwards.

The vertebra causing the most conspicuous prominence, or the vertebra prominens, is inconstant; although it is usually the seventh cervical, it may be the first or even the second thoracic.

On either side of the middle line in the thoracic and lumbar regions there is an elongated furrow, called the spinal groove, produced by the prominence of the sacro-spinalis muscle. This groove is best marked in the lower thoracic and upper lumbar regions, and subsides about the level of the third sacral spine. If the subject is not too muscular, the outline of the scapula may be defined, and will be found to extend from the second to the seventh rib. The scapular spine and acromion process are usually readily felt. The root of the spine is on a level with the third thoracic spine, the inferior angle with the seventh rib. The crest of the ilium can be felt at the lower part of the back, its greatest prominence being on a level with the fourth lumbar spine.

Fascia.—The superficial fascia is thick and fatty, and contains the cutaneous nerves and vessels. The deep fascia is thin, membranous, and resistant. It contains no fat, and provides sheaths for the muscles.

Cutaneous Nerves (Fig. 250).—These are most readily found at the level of the deep part of the superficial fascia, the cutaneous vessels serving as a guide to them. They are derived from the posterior primary divisions of the spinal nerves, each of which, with a few exceptions, divides into a lateral and medial branch. In the thoracic region the medial branches of the upper six nerves become cutaneous near the spines of the vertebrae, and extend outwards. The branch ol the second is especially long, and can be traced outwards over the scapula. The lateral branches of the upper six thoracic nerves end in the muscles of the back. The medial branches of the lower six thoracic nerves are distributed to muscles only, lateral branches becoming superficial along a line following the angles of the ribs. In the lurnbay region the medial branches end in the muscles. The lateral branches of the first three nerves furnish cutaneous offsets which descend over the iliac crest in front of the outer border of the sacro-spinalis to the skin in the gluteal region, supplying in their course the skin of the lumbar region. The lateral branches of the lower two nerves end in the deep muscles.



Fig. 250. — The Cutaneous Nerves and the Superficial Muscles of the Back.


The cutaneous arteries accompanying the cutaneous nerves of the thoracic and lumbar regions are derived from the posterior branches of the intercostal and lumbar arteries.

Muscles — The Trapezius (Fig. 250).—This muscle is so named because, together with its fellow, it presents a four-sided appearance. (The two muscles have also been likened to a monk’s hood or cowl; hence the name cucullaris.)

Origin. — The inner third of the superior nuchal line of the occipital bone, and the external occipital protuberance; the ligamentum nuchae; and the spinous processes and supraspinous ligaments of the last cervical, and, as a rule, of all the thoracic vertebrae. The origins of the two muscles are markedly tendinous between the second cervical and third thoracic spines, where they give rise to an elliptical area, the speculum rhomboideum , widest opposite the sixth cervical spine.

Insertion. — The posterior border of the outer third of the clavicle; the inner border of the acromion process, and upper lip of the posterior border of the spine of the scapula; and the tubercle marking the inner end of the spine. To this tubercle is attached a tendon in which all the fibres of the lower part of the muscle end; it forms the apex of a smooth triangular surface upon which the tendon glides, a bursa intervening between them.

Nerve-supply. — The accessory and a nerve derived from the third and fourth cervical spinal nerves. The two nerves are to be found at the anterior edge of the muscle some little distance above the clavicle. They pass on to its deep surface, where they both branch, the branches joining one another to form a network, the subtrapezial plexus, from which terminal twigs pass into the substance of the muscle.

The upper fibres of the muscle are directed downwards, outwards, and, twisting upon themselves, gain the front of the neck, where they are attached to the clavicle; the middle fibres pass more or less horizontally outwards to the scapular spine; and the lower fibres pass upwards and outwards, ending in the tendon attached to the tubercle of the spine.

Action. — The upper fibres elevate the outer end of the clavicle and the point of the shoulder. If the shoulder be fixed they draw the head downwards, and rotate it to the opposite side. The middle fibres approximate the scapula to the spine. The lower fibres are largely concerned in rotating the scapula in such a way that when they pull the inner end of the spine downwards th,e glenoid cavity at the outer extremity of the bone is elevated.


Ligamentum Nuchse is a fibrous band, or intermuscular septum, occupying the median line of the neck. It is attached above to the external occipital protuberance, and to the external occipital crest below to the spine of the seventh cervical vertebra. Deeply it is attached to the spines of the cervical vertebrae from the second to the sixth. Between the spines it is continuous with the interspinous ligaments.

Latissimus Dorsi (Fig. 250)— Origin. —The spinous processes and supraspinous ligaments of the lower six thoracic vertebrae; the posterior lamina of the lumbar fascia by means of which it is attached to the lumbar and sacral spines and the posterior fourth of the outer lip of the iliac crest; by muscular fibres from the outer lip of the iliac crest for about 2 inches; the outer surfaces of the last three or four rib lateral to their angles by fleshy slips, which interdigitate with slip of the obliquus externus abdominis; and inconstantly from the bad of the inferior angle of the scapula.

Insertion. — The floor of the bicipital groove of the humerus abou its middle third for about i J inches.

Nerve-supply. — The nerve to latissimus dorsi (long subscapular from the posterior cord of the brachial plexus, its fibres being derivec chiefly from the seventh cervical nerve. The nerve enters the muscl< on its deep aspect.

The upper fibres of the muscle pass horizontally outwards, anc cross the inferior angle of the scapula, which they strap to the chesi wall; the succeeding fibres pass obliquely upwards and outwards and those from the iliac crest and lower ribs pass almost verticall} upwards.

Action. — The arm being raised, the muscle draws it downward* and backwards, rotating it inwards at the same time. When the arm is fixed it can raise the trunk, as in the act of climbing a pole. It also elevates the last three or four ribs, as in forced inspiration.

At the inferior angle of the scapula the muscle lies behind the teres major; as it passes outwards and forwards it winds round the lower border of this muscle, and eventually lies in front of it. Intervening between the tendons of the two muscles, close to their insertions, is a synovial bursa. Between the upper border of the latissimus dorsi, the lower border of the trapezius, and the base of the scapula, is a triangular area, the auscultation triangle, in which are exposed a portion of the rhomboideus major, the sixth rib, and the sixth intercostal space. The anterior border of the latissimus dorsi, between the iliac crest and last rib, may overlap the posterior border of the obliquus externus abdominis. Should this not be the case, there is a small triangular area, the lumbar triangle {Petit ), between the two muscles. It is bounded in front by the posterior border of the obliquus externus abdominis, behind by the anterior border of the latissimus dorsi, and below by the iliac crest near its centre. It is covered by skin and fascia only; its floor is formed by a part of the obliquus internus abdominis. In this situation a lumbar hernia may occui, or a lumbar abscess may find its way to the surface.

Levator Scapulae (Fig. 251)— Origin .—By four tendinous slips from the posterior tubercles of the transverse processes of the first four cervical vertebrae.

Insertion. -To the medial border of the scapula from the superior angle to the triangular surface at the root of the spine.

Nerve-supply. Branches of the third, fourth, and fifth cervical

nerves, the last of which is given off in common with the nerve to the rhomboids.

the muscle is directed downwards, backwards, and slightly outwards.

Action. Acting from its origin, the muscle raises the superior angle of the scapula, and rotates the bone in such a way as to depress le point of the shoulder. When the scapula is fixed it is a lateral sxor of the neck.

The levator scapulae may have three or even fewer slips of attachment to le vertebrae. Between it and the serratus anterior is a strong fascial layer presenting the intermediate part of a primitively continuous muscle sheet iund in many animals.


Fig. 251. — The Structures lying deeply to the Trapezius.

)el., deltoid; inf., infraspinatus; L.a.s., levator scapulae; R.M., rhomboideus major; R.m., rhomboideus minor; Sp., splenius; T.M., teres major; T.m., teres minor; Tr., trapezius.

Rhomboideus Minor (Fig. 251)— Origin .—The lower part of the igamentum nuchae, and the spines of, and the supraspinous ligament oetween, the seventh cervical and first thoracic vertebrae.

Insertion .—The medial border of the scapula opposite the triangular surface at the root of the spine.

Rhomboideus Major (Fig. 251)—

Origin . — The spines and supraspinous ligaments of the thoracic vertebrae from the second to the ifth inclusive.


Insertion . — The medial border of the scapula from the triangula surface at the root of the spine to the inferior angle. The insertio takes place by means of a tendinous arcade, which is firmly attache near the inferior angle. This arcade is attached by connective tissu to the greater part of the medial border, from which the muscle ca be detached to a large extent without injury.

Nerve-supply of the Rhomboids. — The nerve to the rhomboids is branch of the fifth cervical. This nerve passes through the scalenu medius, gives a branch to the levator scapulae, and passes downward on the back midway between the middle line and the medial borde of the scapula. It lies deeply to the two rhomboid muscles, into th deep surfaces of which its branches pass.

The direction of the rhomboid muscles is downwards and outwards.

Action. — The muscles draw the scapula backwards and upward' and the lower part of the rhomboideus major, by pulling the lowe angle of the bone upwards and inwards, slightly rotates it, and de presses the point of the shoulder.

Deep Branch of Transverse Cervical Artery (Fig. 251).—Althoug] this vessel, as its name implies, is usually a branch of the transvers cervical, it may arise from the third part of the subclavian. It passe backwards deeply to the levator scapulae, and then downwards unde cover of the rhomboid muscles, lying close to the medial border of th scapula. It gives off branches to the adjacent muscles, and severe offsets to the front and back of the scapula taking part in the scapula anastomosis.

At the upper border of the scapula a limited view is obtained c the inferior belly of the omo-hyoid muscle, and the suprascapula vessels and nerve. The former arises from the upper border of th bone to the inner side of the suprascapular notch, as well as fror the suprascapular or transverse ligament bridging the notch. The suprascapular artery passes to the supraspinous fossa above th ligament, and the suprascapular nerve below it. The artery in thi part of its course furnishes an acromial branch to the upper surfac of the acromion process. The transverse cervical artery is seen, a a higher level than the suprascapular, dividing into superficial an< deep branches. The former passes upwards superficially to the levato scapulae, the latter downwards and backwards deeply to it. Lyin| deeply to the muscles associated with the scapula are the followinj structures:

Serratus Posterior Superior (Fig. 253)— Origin. —The lower part 0 the ligamentum nuchae, and the spines and supraspinous ligament of the last cervical and first two thoracic vertebrae.

Insertion. By fleshy and tendinous slips into the upper border and outer surfaces of the second, third, fourth, and fifth ribs, latera to their angles.

Nerve-supply. —The second, third, and fourth intercostal nerves the origin of the muscle is by a very thin aponeurosis which occupies about half its length. The direction of the fibres is downwards and itwards.

Action. —The muscle elevates the ribs into which it is inserted, id is therefore a muscle of inspiration.

Serratus Posterior Inferior (Fig. 253)— Origin .—The posterior mina of the lumbar fascia, by means of which the muscle is attached the spines and supraspinous ligaments of the lower two thoracic and >per two or three lumbar vertebrae.

Insertion. —By four fleshy slips unto the lower borders of the last ur ribs.

Nerve-supply. —The ninth, tenth, and eleventh intercostal nerves.

The serrations of insertion overlap each other from above downards; the second is the broadest, and the third to a large extent canceals the fourth. The direction of the fibres is upwards and utwards.



Fig. 252.— Diagram of the Lumbar Fascia.


Action. —Draws backwards and slightly depresses the lower four bs, the effect of which is to increase the capacity of the lower part f the thoracic cavity; it fixes the lower four ribs, and thus acts as an uxiliary to the diaphragm. In either case it acts as a muscle of ispiration.

Posterior Lamina of the Lumbar Fascia (Fig. 252).—The lumbar iscia is composed of three laminae— anterior, middle, and posterior, tie latter of which alone is fully exposed in this region. It is of contderable strength, and is attached to the spines of the lumbar and acral vertebrae, and the posterior fourth of the outer lip of the iliac rest. It affords origin to a portion of the latissimus dorsi and to the erratus posterior inferior, and lies behind the sacro-spinalis, forming the posterior wall of its sheath. At the outer border of the sacn spinalis it blends with the middle lamina, which may be partial] seen by raising this border. Superiorly it is joined by the thorac part.

The Thoracic Part of the Lumbar Fascia.—This is a thin aponeurotic sheet which covers the sacro-spinalis in the thoracic region. Its fibr< are chiefly arranged transversely, being attached medially to the spine of the vertebrae, and laterally to the angles of the ribs. Super-adde to the transverse fibres there are a few which are longitudina Superiorly the aponeurosis passes deeply to the serratus posteric superior, and becomes continuous with the deep cervical fascia ensheatl ing the splenius. Interiorly it blends with the posterior lamina of tl lumbar fascia.

Splenius (Fig. '253).—This muscle is so named because it strap or binds down the muscles beneath it. It has a continuous origii but subdivides into two parts—splenius capitis and splenius cervicis.

Origin. —The lower two-thirds of the ligamentum nuchae, and th spines of the last cervical and first six thoracic vertebrae.

Insertion —Splenius Capitis.—The hinder and lower part of th outer surface of the mastoid process, and the outer third of the superic nuchal line of the occipital bone, below the attachment of the sternc mastoid, deeply to which it lies. Splenius Cervicis.—The posteric tubercles of the transverse processes of the first two or three cervicc vertebrae, behind the levator scapulae, and in line with the costc cervicalis.

Nerve-supply .—The posterior primary divisions of the cervica nerves below the third, and of the upper five thoracic nerves.

The muscle is a thin, finely fasciculated sheet, the direction c whose fibres is upwards and outwards.

Action. —The muscle extends the head, is a lateral flexor of the neck and rotates the head to the same side.

Sacro-spinalis (Erector Spinae) ( vide Fig. 253).—This composite muscle is single below in the region between the last rib and iliac crest where it is tendinous medially and fleshy laterally.' Extending up wards, it subdivides into three longitudinal columns—outer, middle and inner; there are three muscles in each of the outer and middl columns, and one in the inner column, making seven muscles in all.

Origin. The spines of the last two thoracic, all the lumbar, am the upper four sacral vertebrae; the back of the fourth sacral vertebra the posterior sacro-iliac ligament; and the posterior fifth of the ilia< cr f?.The insertion of the muscle is represented by the columns int( which it divides. Near the last rib it presents a surface groove, in c icatmg its subdivision at this level into an outer and inner column t tie latter subdividing into the middle and inner columns.

The Lateral Column (the Ilio-costo-cervicalis) is composed of three muscles the ilio-costalis, the costalis, and the costo-cervicalis ir succession from below upwards.

The Ilio-costalis is the direct continuation of the outer part of angles of the ribs from the seventh to the eleventh, and from the outer rrface of the twelfth rib; it is inserted by tendons into the angles of he upper ribs from the second to the sixth, and into the outer border f the first rib lateral to the tubercle.


Fig. 253. — The Post-vertebral Musculature.

n the left not dissected, but on the right dissected to some extent, splenius and semispinalis capitis having been removed to expose suboccipital structures.


The Costo-cervicalis (Cervicalis Ascendens) {vide Fig. 253) is the Dntinuation of the costalis upwards into the neck. It arises by tendin

e sacro-spinalis, and is inserted into the lower border of the twelfth ), and by fleshy and tendinous bundles into the angles of ribs from e seventh to the eleventh.

The Costalis (Musculus Accessorius) {vide Fig. 253) prolongs the o-costalis from the lower six to the upper six ribs. It arises by ndons, medial to the slips of insertion of the ilio-costalis, from the


ous slips from the third, fourth, fifth, and sixth ribs, medial to tb tendons of insertion of the costalis; it is inserted into the posteric tubercles of the transverse processes of the fourth, fifth, and sixt cervical vertebrae, where it is in line with the splenius cervicis.

Action. —The muscles of the outer column are extensors and laten flexors of the vertebral column; they also depress the ribs and aid i expiration.

The Intermediate Column (the Longissimus) consists of three muscle —the longissimus thoracis, the longissimus cervicis, and the longis simus capitis, in order from below upwards. _ ;

The Longissimus Thoracis is the direct continuation of the inne part of the sacro-spinalis, and is inserted in a twofold manner. Th inner insertions are by round, tapering tendons attached to the ac cessory processes of the lumbar vertebrae and the extremities of th transverse processes of the thoracic vertebrae. The outer insertion are fleshy, and are attached to the backs of the transverse processe of the lumbar vertebrae, and to the outer surfaces of the lower ten rib lateral to the tubercles.

The Longissimus Cervicis (Transversalis Cervicis) is the continuatio

of the longissimus thoracis into the neck. It arises from the transvers processes of the upper five or six thoracic vertebrae, and is inserte into the posterior tubercles of the transverse processes of cervica vertebrae from the second to the sixth inclusive, where it is media to the splenius cervicis and costo-cervicalis.

The Longissimus Capitis (Trachelo-mastoid) [vide Fig. 253) is th continuation of the longissimus thoracis to the head. It arises fror the transverse processes of the upper five or six thoracic vertebrae ii close connection with the longissimus cervicis, and from the articula processes and capsular ligaments of the lower three cervical vertebra It is inserted into the lower and hinder aspect of the mastoid proces under cover of the splenius capitis. The muscle is very narrow an< ribbon-like, and near its insertion is crossed by a tendinous inter section.

Action .—The muscles of the middle column are extensors and latera flexors of the vertebral column. They also extend the head, flex th neck to one side, and rotate the head to the same side.

The Medial Column (the Spinalis) consists chiefly of the spinali thoracis, which is intimately associated with the inner part of th longissimus dorsi. It arises from the lower two thoracic and uppe two lumbar spines, and is inserted by tendinous slips into the uppe thoracic spines—sometimes the upper four, sometimes as many as th upper eight.

Action. —Extends the thoracic portion of the vertebral column.

A erve-suppiy. —The sacro-spinalis and its component muscles an supplied by the posterior primary divisions of the spinal nerves.

Between the iliac crest and the last rib the sacro-spinalis is enclosec in a sheath, the posterior wall of which is formed by the posterio lamina of the lumbar fascia, the anterior wall by the middle lamin; this fascia. On the back of the sacrum its tendon gives origin 3eply to fibres of multifidus.

Semispinalis Capitis (Complexus) — Origin .—'The extremities of the ansverse processes of the upper six thoracic and last cervical vertebrae, id the backs of the articular processes and capsular ligaments of iree or four cervical vertebrae above the seventh. The muscle may iceive a fleshy slip from the spine of the seventh cervical.



Fig. 254.-—The Deep Muscles of the Back.

Insertion .—The occipital bone between the superior and inferior luchal lines, extending outwards for about 2 inches from the occipital 'rest. About the level of the sixth cervical vertebra the inner part )f the muscle is interrupted by a tendinous intersection, and from this

'ircumstance is known as the biventer cervicis. .

Nerve-supply .—The posterior primary division of the first cervical 3 r suboccipital nerve; the greater occipital; and the posterior primary divisions of cervical nerves below the second.



The innermost and longest fibres pass almost vertically upward: the outer and upper fibres are short and pass upwards and inwards.

Action .—Both muscles extend the head; one muscle inclines it t one side and rotates it to the opposite side.

A small part of the semispinalis capitis may appear superficially i the upper part of the posterior triangle of the neck. The greate occipital nerve passes through the upper part of the muscle. Imme diately below the occipital bone it covers the rectus capitis posteric


Semispinalis Cervicis...


Semispinalis Thoracis


Longissimus Capitis


- Longissimus Capitis -Transversalis Cervicis


Longissimus Thoracis (turned outwards)


t' IG - 2 55- tHE Middle Column of the Sacro-spinalis and the

Semispinales Muscles.


majoi and minor and the superior and inferior oblique muscles supe: dally, and forms the roof of the suboccipital triangle.

emispinalis Thoracis (Fig. 255)— Origin .—The extremities of th

rans verse processes of the thoracic vertebrae from the sixth to th tenth inclusive.

Insertion.-—The spines of the last two cervical and upper for thoracic vertebrae.

tr,,, SemlSPinaliS Cervi ® is ( Fi S- 255)— Origin .—The extremities of th transverse processes of the upper five thoracic vertebrae.



Insertion .—The spines of the cervical vertebra from the second > the fifth inclusive.

The bundle of fibres inserted into the spine of the axis is the largest, nd the bundles overlap one another from above downwards.

Nerve-supply of the Semispinales .—The posterior primary divisions E the cervical and upper thoracic nerves.

The fibres of the two muscles are directed upwards and inwards.


Fig. 256. — The Multifidus Spin^ and Levatores Costarum Muscles.


Action .—The muscles are extensors and lateral flexors of the vertebral column. The semispinalis cervicis and the cervical portion >f the semispinalis thoracis also rotate the cervical vertebrae towards he opposite side.

Multifidus (Fig. 256) lies deeply in the groove by the sides of the pines of the vertebrae.

Origin .—The sacral groove and the deep surface of the tendon of he sacro-spinalis; the posterior sacro-iliac ligament and the hinder part






of the inner lip of the iliac crest; the mammillary tubercles of th lumbar vertebrae; the transverse processes of the thoracic vertebrae and the articular processes of the lower four cervical vertebrae.

Insertion .—The spines of the vertebrae from root to tip.

The superficial fibres from any given origin pass over three or fou: vertebrae before obtaining insertion, the succeeding fibres pass ove two or three vertebrae, and the deeper fibres pass over one.

Nerve-supply .—The posterior primary divisions of the spinal nerves

Action. —An extensor and lateral flexor of the spinal column, a the same time rotating the cervical and thoracic regions towards thi opposite side.

The fibres of multifidus, semispinalis thoracis, and semispinalis cervicis a] pass obliquely upwards and medially from the transverse processes to the spinou processes; they together form the semispinalis group of muscles.

The Rotatores (Fig. 256) are confined to the thoracic region, and an eleven in number.

Origin . — The upper and back part of a transverse process.

Insertion. — The lower border of the lamina of the vertebra imme diately above.

Nerve-supply . — The posterior primary divisions of the spinal nerves

Action . — Rotate the vertebrae towards the opposite side.

The Interspinales are usually confined to the cervical and lumbai regions, but may be found at either end of the thoracic region. The} are arranged in pairs between the successive spines, the two slips bein^ disposed one on either side of the interspinous ligament. In the neck they are limited to the region of the apices of the spines, but in the lumbar region they extend for nearly their whole length.

Nerve-supply . — Posterior primary divisions of the spinal nerves.

Action . — Extend the vertebrae.

The Intertransversales occur chiefly in the cervical, but also occur in the lower thoracic region and lumbar regions. They are arranged in pairs in each interspace, one muscle lying in front of the other. Ir the neck they extend between the anterior and posterior tubercles oi adjacent vertebrae. In the lumbar region the muscles maybe arranged in pairs, but are, as a rule, undivided. In this region they may be absent and replaced by membrane.

Nerve-supply. — Posterior primary divisions of the spinal nerves.

Action. The muscles are lateral flexors of the successive vertebrae.

The Levatores Costarum (Fig. 256) are twelve in number on either side.

Origin. — The highest muscle arises from the tip of the transverse process of the seventh cervical vertebra, and the succeeding eleven arise from the tips of the transverse processes of the thoracic vertebrae from the first to the eleventh inclusively.

Insertion. Each muscle is inserted into the outer surface of the rib below, extending from the tubercle to the angle. In the case ol the lower two or three muscles the more superficial fibres passing over one rib are inserted into the rib next below it, these fibres constituting he levatores costarum longiores.

Nerve-supply .—The intercostal nerves.

The muscles are directed downwards and outwards.

Action .—Elevate the ribs, and are therefore muscles of inspiration.

Each muscle is somewhat fan-shaped, and contains an admixture )f aponeurotic fibres. The direction of the muscle fibres coincides vith that of the external intercostals, with which their outer borders ire closely associated.

Posterior Primary Divisions of the Spinal Nerves. —In the thoracic region these nerves pass backwards through a four-sided space bounded below by the neck of a rib, above by the transverse process of the upper vertebra, externally by the superior costo-transverse ligament, and medially by the body of a vertebra. Between the transverse processes each nerve divides into a medial and lateral branch. The medial branches incline inwards on the superficial surface of multifidus, and the upper six become cutaneous near the spines of the vertebrae, whilst the lower six end in the deep muscles. The lateral branches pass outwards beneath the middle column of the sacro-spinalis, and, on reaching the interval between the middle and outer columns of that muscle,, end differently in the upper and lower parts of the back. The upper six end in the deep muscles, but the lower six become cutaneous along the line of the angles of the ribs. In the lumbar region the posterior primary divisions pass backwards, each through a space bounded laterally by the quadratus lumborum muscle, medially by the intertransversalis muscle, and above and below by a transverse process, the medial branch occupying a groove between the mammillary and accessory processes of the vertebra. 1 heir further disposition is similar to that in the lower thoracic region, but the lateral branches of the first three only furnish cutaneous nerves, and these are mainly distributed to the skin of the gluteal region.

The arteries of the thoracic region are the posterior branches of the intercostal arteries. Each posterior branch passes backwards in company with the corresponding posterior primary division of a spinal nerve. Before passing through the quadrangular space it gives off a lateral spinal branch, which enters the spinal canal through the intervertebral foramen. Passing backwards, the trunk of the artery divides into medial and lateral branches, which have a distribution similar to that of the corresponding branches of the nerve.

The veins of the thoracic region terminate in the intercostal veins.

The arteries of the lumbar region are the posterior branches of the lumbar arteries. Each accompanies the corresponding posterior primary division of a spinal nerve, and its distribution is comparable to that in the thoracic region.

The veins of the lumbar region terminate in the inferior vena cava,


The Pectoral Region and Axillary Space.

Landmarks.—The outline of the clavicle and acromion process of the scapula are readily defined. The acromial epiphysis may remain permanently detached from the spine and simulate a fracture. The roundness of the shoulder is largely due to the deltoid muscle, but also in part to the head of the humerus. Below the middle of the clavicle is a depression, the infraclavicular fossa, corresponding to an interval between the deltoid and pectoralis major. In this region it is possible to compress the axillary artery against the second rib, but very firm pressure is required. Below the outer part of the clavicle the tip of the coracoid process, which is here covered in front by the deltoid, may be felt as a somewhat obscure rounded knob. If the arm is raised from the side, at right angles to the trunk, the coracobrachialis muscle is rendered prominent. In this position the course of the axillary artery is indicated by a line drawn from the middle of the clavicle to the inner edge of the muscle. The hollow of the armpit, indicating the position of the axillary space, is bounded in front and behind by the axillary folds. The anterior axillary fold is usually at the level of the fifth rib, and is caused by the prominent lower edge of the pectoralis major; the posterior fold is at a lower level, and corresponds to the lower edge of the latissimus dorsi. In the female the mammary gland causes a more or less well-marked rounded prominence on the front of the chest. A little below and medial to the centre of the mammary prominence is the nipple, which is surrounded by a pigmented circular area—the areola. The exact position of the nipple is subject to variation. As a rule it corresponds to the fourth intercostal space about 4 inches from the mid-sternal line, but in corpulent persons, and in females with pendulous mammae, it is lower in position. In the middle line the sternum can readily be made out, and about 2 inches below its upper border a transverse ridge, or sternal angle, may be felt. This ridge serves as a guide to the position of the second costal cartilage on either side. Above the upper border of the sternum is the suprasternal depression. Below the lower border of the body of the sternum is an infrasternal depression, situated between the seventh pair of costal cartilages, and marking the position of the xiphoid process.

The Cutaneous Nerves are arranged in three groups—supraclavicular, anterior, and lateral branches of intercostal nerves.

The supraclavicular nerves are branches of the cervical plexus, and are derived from the third and fourth cervical nerves. They are three in number medial, intermediate, and lateral branches. As they descend from the neck they lie deeply to the platysma myoides. The medial branch crosses the sterno-clavicular joint, and is distributed to the skin covering the upper part of the sternum. The intermediate branch, consisting usually of two or more nerves, crosses the middle part of the clavicle, and is distributed to the skin covering the front ol the chest, the lateral branch crosses the acromion process, and is distributed to the skin covering the upper part of the leltoid.

The anterior cutaneous nerves are the terminal branches of the ipper six intercostal nerves, and become superficial by passing through he pectoralis major close to the sternum. Small medial twigs supply he skin covering the sternum; larger lateral branches supply the


Fig. 257. — Cutaneous Nerves of the Trunk (Antero-lateral View) (after Henle).

1-12, anterior cutaneous; 2-12, lateral cutaneous.

skin covering the pectoralis major. The branch of the first intercostal nerve is sometimes absent.

The lateral cutaneous nerves are branches of the intercostal nerves from the third to the sixth inclusively. The first intercostal nerve has no lateral cutaneous branch. The lateral cutaneous of the second intercostal nerve is the intercosto-brachial nerve, which crosses the axillary space to the arm. The succeeding lateral cutaneous nerves escape from their respective intercostal spaces by passing through the external intercostal muscles not far from the lower border of the pectoralis major. Each divides into anterior and posterior branches, which pass out between the digitations of the serratus anterior, the two being separated, each from the other, by a slight interval. The anterior branches wind round the lower border of the pectoralis major, and supply skin in the pectoral region; the posterior branches pass backwards, and supply the skin on the side wall of the chest.

The anterior and lateral cutaneous nerves are accompanied by arteries, the anterior being the perforating branches of the internal mammary, and the lateral being branches of the intercostal arteries.

Fascia.—The superficial fascia is continuous over the clavicle with the superficial fascia of the neck, and is noteworthy in two respects. In the first place, just below the clavicle it has a faintly reddish colour, due to the fact that over the clavicular portions .of the pectoralis major and deltoid it contains fibres of the platysma, which can be seen on incising it. In the second place, in the region of the mammary gland it divides into two laminae, which ensheathe that gland. From these laminae processes pass into the substance of the gland supporting its lobes. From the anterior lamina fibrous bands pass to the skin, these being known as the ligamenta suspensoria of Cooper. Interiorly the superficial fascia is continuous with that covering the anterior abdominal wall.

The deep fascia is thin and membranous, and closely invests the pectoralis major. Superiorly it is attached to the front of the clavicle, medially it is fixed to the front of the sternum, laterally it is continuous with the deep fascia over the deltoid, and interiorly at the lower border of the pectoralis major it joins the axillary fascia.

d he axillary fascia stretches from the anterior to the posterior fold of the axilla, and forms the floor of the space. It is continuous in front with the deep pectoral fascia, and behind it blends with the deep fascia covering the latissimus dorsi. Laterally it is continuous with the deep fascia of the arm, and medially with the fascia covering the serratus anterior. It domes upwards into the axilla, its convexity being maintained by the deep pectoral fascia (vide p. 420). The axillary fascia is not a continuous membrane, but exhibits deficiencies through which the superficial fascia of the pectoral region is directly continuous with the fatty tissue filling the axillary space.

The Mammary Gland (Fig. 258) is situated on the surface of the pectoralis major. It is somewhat hemispherical, and extends vertically from the second to the sixth rib, and transversely from the side of the sternum to the anterior fold of the axilla, except below and laterally, where it extends beyond that fold and rests upon the serratus anterior and external oblique muscles. There is no fat beneath the nipple and areola, the skin of these parts being provided with plain muscular tissue disposed circularly. The contraction of the muscle fibres compresses the veins, and erection of the nipple is the result. The summit of the nipple is perforated by the openings of the lactiferous ducts, fhe skin of the areola presents a number of small projections due to ebaceous glands, known as the glands of Montgomery. The mamma 3 a compound racemose gland, which is composed of about twenty obes, these in turn consisting of lobules all being embedded in a fibrous troma. The entire gland is ensheathed by the splitting of the supericial pectoral fascia into two laminae, which send processes into its nterior supporting its component lobes. The posterior layer of the heath is loosely connected to the deep pectoral fascia covering the lectoralis major, and occasionally deep processes of the gland penetrate nto the substance of the muscle. The lobes are pyramidal, and their ipices converge toward the nipple. Each lobe is distinct, and has ts own duct. A lobe is composed of lobules, each lobule consisting


Fig. 258. —The Female Mamma during Lactation (after Luschka).

)f a cluster of tubes, called alveoli or acini, which represent the secretng parts of the gland, and are lodged in spaces known as loculi. The ilveolar tubes are lined with cubical epithelium, the cells of which contain fat globules during the period of the functional activity of the )rgan. The ducts of the lobes are about twenty in number, and are called the lactiferous or galactophorous ducts. They are lined with columnar epithelium, and as they approach the nipple each presents 1 dilatation, called the sinus or ampulla. Terminally each duct becomes narrow, and enters the nipple to open by a minute pore on its summit. Hie mammary glands are present in both sexes, but in the male their ievelopment is, as a rule, arrested, and they are in a rudimentary condition.

Blood vessels of the Mamma. — The arteries are the external mammary branches of the lateral thoracic artery from the second part of t. axillary; the anterior cutaneous or perforating branches of the intern mammary; and branches from the intercostal arteries.

The veins join the axillary and internal mammary veins.

Lymphatics—The principal lymphatic vessels of the mamma: gland arise injthe fibrous stroma, lie between the galactophoroi ducts, and converge towards the nipple. In the region around t] nipple they terminate beneath the areola in a network, the subareol plexus. This plexus also receives the cutaneous lymphatics of t] nipple and areola. The efferent vessels from this plexus pass to tl pectoral group of axillary glands, more particularly to those on a lev with the third rib.

There are, however, other paths by which lymph is conveyed awe from the mammary gland. Some lymphatic vessels emerge from abo the outer two-thirds of the gland, and pass to the pectoral group of axilla] glands, either directly, or after having joined the principal lymphatic Other vessels (one or more) draining the deep and upper part of tl gland terminate in the infraclavicular glands. A third set of lymphati* emerging from about the inner third of the gland pass backwards wil the perforating branches of the internal mammary artery through tl intercostal spaces close to the edge of the sternum, and join the med astinal glands.

The Nerves are derived from the supraclavicular branch of tl cervical plexus, and the anterior and lateral cutaneous branches ( the upper intercostal nerves.

Accessory mammae are sometimes met with on the upper, lowe: and inner outskirts of the main gland, more rarely in the axilla, o the anterior abdominal wall, or in the groin.


Structure of the Mamma. —The mammary gland belongs to the class acmo-tubular or compound racemose glands. It consists of glandular tissi and a fibrous connective-tissue stroma, which together constitute a firm, ligh red mass, known as the corpus mammcB .

- The glandular element is composed of large lobes, varying in number fro fifteen to twenty. Ihere is no firm fibrous capsule, such as that possessed 1 tne parotid salivary gland, but from the superficial pectoral fascia, within whic rut ]^ mmar y gl an d is embedded, fatty processes project between the lobe e fibrous tissue of these processes being continuous with the sustentacul; issue ol the gland.. Each lobe is tapering in outline, and is provided with i nipple' vaiaous Idbes being disposed in a radiating manner from th

ff mammary lobe is composed of smaller lobes, each small lobe consisting <

group o lobules, the structure of which furnishes the key to the structure < the entire gland.

mai J im ary lobule consists of from one to three acini , provided with \ acb TT 1S duct is one of the radicles of the main duct of a give

obe * The radicle duct breaks up into two or three somewhat dilate

^ , r T passages, the walls of each of which are convoluted. This convolute n i G j ls r ue f° the fact that the walls are distended into a series of pouche: pnH fu, V f° b .which beset all parts of the wall of the acinus, including its case£

ariuu* ‘,J> lvln S ^ somewhat of the appearance of a grape—hence the nam

whir Vi ic u 6 ^ each alveolus consists of a delicate basement membrane

v es b y capillary blood vessels, and lined with cubical or show columnar epithelium. From one to three acini constitute a lobule, and they are onsequently appendages of a lobular duct. Contiguous lobular ducts unite nd form the duct of a small lobe, and the contiguous ducts of small lobes unite nd form the duct of a large lobe. The number of main ducts corresponds to he number of main lobes—namely, from fifteen to twenty. They are referred o as the lactiferous or galactophorous ducts. The main lactiferous ducts conerge towards the nipple. As they lie beneath the areola, each duct expands ito a somewhat spindle-shaped dilatation, called the ampulla or lactiferous inus, which serves as a reservoir for the milk during lactation. Terminally, he duct becomes narrow, and having traversed the nipple, opens upon its summit t the bottom of a small depression or foveola. The orifice of the duct is of mailer size than the excretory tube leading to it. The arrangement of orifices t the summit of the nipple may be compared to the arrangement of the orifices f the excretory tubes of the kidney at the apex of a Malpighian pyramid.

The walls of the ducts consist of areolar and elastic tissue, and they are lined nth columnar epithelium. The elastic tissue is disposed both longitudinally nd in a circular manner.


Fig. 259. — Sections across Mammary Ridges at 8 and 12 Mm.

Other two sections show slow enlargement during second and third months.


Development of the Mammary Glands. — The mammary glands are of ectodermic origin. In the course of the second month of intra-uferine life a circular hickening of the epidermis (ectoderm) makes its appearance in the region of he future gland. This thickening projects into the subjacent mesoderm, and lie superficial central cells of the thickening being shed the thickened area is ow depressed. From the deep surface of the thickened ectodermic area solid olumns of cells grow into the subjacent mesoderm and give off lateral branches, hese cell columns become hollow, and form the lactiferous or galactophorous ucts, which open upon the area corresponding to the circular thickening of pidermis. The lateral offshoots of the cell columns give rise to the lobes, )bules, and alveoli or acini of the gland, each lateral offshoot thus giving rise 3 a mammary gland in miniature.


The nipple and areola are developed from the glandular area—that is to ay, the area of the original thickening of epidermis. The depression of this rea disappears, and its central portion becomes elevated to form the nipple, his contains the terminal parts of the lactiferous ducts, bloodvessels, and onnective tissue. The remainder of the glandular area forms the areola, he corium corresponding to the nipple and areola is provided with unstriped muscular tissue.

The connective-tissue stroma of the gland is developed from mesoderm into mich the outgrowths penetrate.


Pectoralis Major (Fig. 260)—

Origin . — The anterior surface of th inner part of the clavicle, and the anterior sterno-clavicular ligament the anterior surface of the sternum as low as the xiphoid process the anterior surfaces of the upper six costal cartilages, and slight! from the bony part of the sixth rib; and the upper portion of th aponeurosis of the external oblique.

Insertion . — The lateral lip of bicipital groove of the humerus.

The muscle is subdivided by a more or less definite interval inb two parts, an upper or clavicular and a lower or sterno-costal.



Fig. 260.—The Superficial Muscles of the Front and Inner Side of the Pectoral and Brachial Regions.

The tendon of insertion is so folded upon itself as to present in section the appearance of an inverted V, and is therefore composed of two layers, anterior and posterior, the former of which is vertically the shorter, the two being continuous with one another below. The anterior layer receives the sterno-costal fibres above the third costal cartilage, and superficially the clavicular fibres, which, descending to a lower level than the other fibres of the muscle, are intimately connected at their insertion with the tendon of the deltoid. The posterior layer receives all the fibres from the third costal cartilage downwards; these fibres, as they pass outwards and upwards, twist upon themselves, nd round the lower border of the muscle, and gain its deep aspect,’ here they ascend to the posterior layer of the tendon, the lowest )res being continuous with its upper end, the highest fibres with its wer end. The posterior layer ascends on the outer bicipital lip to higher level than the anterior, and from its upper border a tendinous expansion spreads across the upper end of the bicipital groove, and bends upwards to the capsular ligament of the shoulder-joint.

om the lower border of the tendon an expansion extends downwards the deep fascia of the arm.


g. 261.—A Diagrammatic Sagittal Section through the Anterior Wall of the Axilla to illustrate the Dispositions of the Deep Pectoral Fascia, the Clavi-pectoral Fascia, and the Structures traversing the Latter.

Nerve-supply .—The lateral pectoral from the lateral cord of the achial plexus (its fibres coming from the fifth, sixth, and seventh rvical nerves)—the branches of this nerve enter the deep surface of e clavicular and upper sterno-costal portions; and the medial pectoral, e branches of which enter the deep surface of the sterno-costal portion, ter having passed though the pectoralis minor.

The upper fibres pass downwards and outwards, the middle transrsely outwards, and the lower upwards and outwards.

Action . — Adducts the arm and rotates it inwards. The clavicular rtion pulls the arm forwards, or flexes the shoulder-joint. If the n is fixed, it can raise the trunk, this action coming into play when climbing a pole; it can also elevate the upper ribs, and is one of th muscles concerned in forced inspiration.

The upper border of the muscle is related to the deltoid, from whicl it is separated by a triangular interval for a short distance below th clavicle, the cephalic vein, the deltoid branch of the acromio-thoraci artery, and the infraclavicular glands intervening between the two.

A small variable muscle, the sternalis, is sometimes present on one or bot sides. It is more or less vertically disposed, lying in front of the pectoral major, close to the sternum. Its disposition and attachments are very in constant.

The Deep Pectoral Fascia (Fig. 261) is situated on the deep aspec of the pectoralis major, taking part in the formation of the deep laye of its sheath. Above it consists of two layers ensheathing the sub clavius, and attached to the anterior and posterior lips of the sub clavian groove on the inferior surface of the clavicle. A single laye between the subclavius above and the pectoralis minor below it en sheathes the latter muscle, and is thence prolonged downwards fron its lower border to the axillary fascia, with which it blends. The lowe part is known as the suspensory ligament of the axilla.

The Clavi-pectoral Fascia is that part of the deep pectoral fasci; which occupies a triangular interval (Fig. 264), bounded above by th subclavius, below by the upper edge of the pectoralis minor, and a the apex of which is the coracoid process. The upper part of th membrane is thick and resistant, and presents, when artificially de fined, a well-marked curved lower edge arching from the sternal en< of the first rib to the coracoid process. This arched band is know] as the costo-coracoid ligament. Below the costo-coracoid ligamen the membrane is loose and fatty; here the cephalic vein, the acromio thoracic artery, the lateral pectoral nerve, and lymphatic vessels pas through it. The clavi-pectoral fascia lies in front of the axillar; vessels, with the sheath of which it is continuous.

The costo-coracoid ligament may represent the ventral end of the coracoi

bar, the dorsal end of which persists as the coracoid process.

Pectoralis Minor (Fig. 262)— Origin.— The upper borders and oute surfaces of the third, fourth, and fifth ribs near their anterior ex tremities, as well as from the fascia covering the adjacent externa intercostal muscles.

Insertion. —The antero-medial border of the coracoid process 0 the scapula and the adjacent portion of its upper surface.

Nerve-supply. —The medial pectoral nerve, a branch of the media cord of the brachial plexus, its fibres being derived from the eightl cervical and first thoracic nerves. The branches of the nerve ente the muscle on its deep surface, and a few of them pass through it t< enter the deep surface of the pectoralis major.

It is a triangular muscle, the direction of which is upwards an< outwards.

Action .—Draws the scapula downwards and forwards, depressing the point of the shoulder. If the shoulder is fixed it raises the ribs, md is thus concerned in forced inspiration.

Subclavius — Origin .—By a rounded, tapering tendon from the jpper surface of the first rib at its junction with its cartilage.

Insertion .—The subclavian groove on the under surface of the


Fig. 262. — The Greater Part of Pectoralis Major has been removed, and the Cut Tendon turned Forward, to expose Pectoralis Minor in Position in the Front Wall of the Axillary Space.

Only muscles are shown.

-lavicle, extending from the rhomboid impression medially to an nterval between the conoid tubercle and trapezoid line laterally.

Nerve-supply .—The nerve to the subclavius, which arises from the ront of the upper trunk of the brachial plexus, its fibres being derived rom the fifth cervical. The nerve descends from the neck behind he clavicle, and enters the deep surface of the muscle.

It is a prismatic muscle directed obliquely upwards and outwards. Action .—Depresses the clavicle.


The Axillary Space is situated between the upper part of the ari and upper part of the thoracic wall. In form it is a four-sided pyrami< and presents an apex, a base or floor, and four walls—anterior, posterio inner, and outer. It is of much greater extent towards the thorac: wall than towards the arm, as the anterior and posterior walls convey from the former to the latter. The apex is the narrowest part of tf space, is truncated, and is directed upwards towards the root of the ned It is a small triangular space lying between the clavicle, the first ril and the upper border of the scapula. The base or floor is of cor siderable extent, and is formed by the axillary fascia, superficial fasci; and skin. The anterior wall is formed by the pectoralis major, togethc with the fascia ensheathing the subclavius and pectoralis minor. Tf posterior wall is formed from above downwards by the subscapulari teres major, and latissimus dorsi. The posterior wall in vertical exterior is longer than the anterior. The inner wall is formed by the uppe four or five ribs, with their intercostal muscles between them, thes structures being covered on their axillary aspect by the serratus anteric muscle. The outer wall is very narrow, and is formed by the uppe part of the shaft of the humerus, clothed by the coraco-brachialis an short head of the biceps.



Fig. 263.— Scheme of a Horizontal Section through the Axilla to illustrate the chief structures constituting its four walls.


Contents. — The axillary vessels and the main nerve trunks gain th axilla by passing through the triangular -interval representing il truncated apex. In the upper part of the space these structures li immediately behind the anterior wall. As they extend downwarc to the arm they cling to the outer wall, but, relatively to the spac< incline backwards, and in its lower part are in contact with the posteric wall. Ihe acromio-thoracic and the lateral thoracic arteries are i close relation with the anterior wall, the former above the pectoral minor, the latter follows the lower border of the muscle. The subscapular artery lies on the posterior wall, and follows the lower border of the subscapularis. The anterior and posterior circumflex arteries are in relation with the posterior wall, but soon leave the space, the latter passing backwards between the subscapularis and teres major, the former passing outwards in front of the humerus.

The lateral pectoral nerve passes through the clavi-pectoral fascia, and enters the deep surface of the pectoralis major. The medial pectoral nerve enters the deep surface of the pectoralis minor, some of its Tranches passing through it to the pectoralis major. The nerve to serratus anterior descends on the inner wall, lying on the serratus anterior. The intercosto-brachial nerve, escaping from the second intercostal space, crosses the axilla to the inner side of the arm. At a lower level a branch of the lateral cutaneous of the third intercostal may also cross the axilla to the inner side of the arm. The two subscapular nerves and the nerve to latissimus dorsi lie upon the posterior wall, and supply the three muscles of which it is formed. The circumflex nerve accompanies the posterior humeral circumflex artery. The radial nerve descends behind the axillary artery. The median nerve is on the outer side of the main artery, and the ulnar nerve is medial to it, between it and the vein. The medial cutaneous nerve of arm is on the inner side of the vein, and the medial cutaneous nerve of forearm is usually in front of the main artery.



Fig. 264. — The Structures exposed to View on reflecting the Clavicular Part of the Pectoralis Major.


The axillary lymphatic glands are disposed in four groups. Th lateral or humeral glands are on the outer wall , in close relation wit] the axillary vein. The pectoral glands follow the lateral thoracic artery at the lower border of the pectoralis minor. The subscapu g an s are on the posterior wall, disposed about the subscapular artei the apical glands are near the apex of the space.



The Axillary Artery is the continuation of the subclavian, and extends from the outer border of the first rib to the lower border of the teres major, where it becomes continuous with the brachial. When the arm is by the side of the trunk, the vessel describes a curve with the convexity upwards, but when the limb is abducted and is at right angles to the trunk, its course is almost straight. The artery is crossed in front by the pectoralis minor, and is thus conveniently divided into three parts.

The First Part extends from the outer border of the first rib to the upper border of the pectoralis minor.

Relations. — Anteriorly it is covered by the subclavius, the clavicular part of the pectoralis major, and the clavi-pectoral fascia. The


Fig. 266.—To illustrate the Relations of Veins and Nerves to the

Axillary Artery.

The two oblique dotted lines indicate the position of the pectoralis minor.

I., II., and III. are placed on the three parts of the artery.

cephalic vein, some of the tributaries of the acromio-thoracic vein, and the communicating loop between the lateral and medial pectoral nerves, also lie in front of it. Posteriorly are the first intercostal space, the first digitation of the serratus anterior, the upper portion of the second rib, the nerve to serratus anterior and the medial pectoral nerve. Laterally, and above it, are the cords of the brachial plexus. Below, and slightly overlapping it, is the axillary vein.

The Second Part lies behind the pectoralis minor.

Relations .—Anteriorly are the pectoralis major and minor muscles. Posteriorly is the posterior cord of the brachial plexus, behind which is a quantity of fat separating the vessel from the subscapularis. Laterally is the outer cord of the brachial plexus. Medially are the inner cord of the brachial plexus, medial pectoral nerve, and th< axillary vein.

The Third Part is the longest part, and extends from the lowei border of the pectoralis minor to the lower border of the teres major.

Relations. — Anteriorly, but at some little distance from it, is th< pectoralis major. As the posterior wall of the axilla is longer thar the anterior, its lower end escapes from under cover of the lower edg< of the pectoralis major and is superficial, being covered in front by skir and fascial layers only. The medial root of the median nerve at r higher level and the medial cutaneous nerve of forearm at a lowei level are in front of it. Posteriorly are the subscapularis, tendor of the latissimus dorsi, the teres major, the circumflex and radia nerves. Laterally are the coraco-brachialis muscle, the outer root 0 the median nerve, and the musculo-cutaneous nerve. Medially i: the axillary vein. Between the axillary vein and the artery are th( medial root of the median nerve, the ulnar nerve, and for a shori distance the medial cutaneous nerve of forearm; medial to the veir is the medial cutaneous nerve of arm.

Branches of the First Part. —The superior thoracic artery is a smal and somewhat variable branch, arising from the deep aspect of the axillary artery, and passing backwards to supply the structure* occupying the first intercostal space; it may send branches to the second intercostal space. The acromio-thoracic artery is a short large trunk arising from the front of the axillary artery above the upper border of the pectoralis minor. It passes forwards througl the clavi-pectoral fascia, and divides into pectoral branches, descending between and supplying the two pectoral muscles; acromial branches passing outwards deeply to the deltoid—some of them pass througl the muscle and ramify on the upper surface of the acromion process where they anastomose with branches of the suprascapular anc posterior circumflex; deltoid (descending humeral) branch passes downwards and outwards with the cephalic vein between the pectoralis major and deltoid, to which muscles it is distributed; clavicular brand passes upwards to end in the subclavius.

The acromio-thoracic artery is sometimes described as arising deeply to th( pectoralis minor, and consequently as a branch of the second part of the axillar) artery. This misconception has arisen from the fact that when the arm if abducted and is at right angles to the trunk, the position in which the axillar} space is studied in the dissecting room, the pectoralis minor is shifted upward; to a considerable extent and overlaps the origin of the vessels. In the anatomica position, however, with the arm hanging by the side of the trunk, the origir is some little way above the upper edge of the muscle.

Branches of the Second Part. —The lateral thoracic artery is directec downwards and inwards, following the lower border of the pectoralis minor to the thoracic wall. It is distributed to the pectoral muscles serratus anterior, and intercostal muscles, and sends external mammary branches which wind round the lower border of the pectoralis major and supply the mammary gland. It supplies the pectoral group 0: axillary glands, and anastomoses with branches of the aortic intercostals and internal mammary. The alar thoracic artery is distributed to the axillary glands. It is seldom an independent branch, and is usually represented by branches of the lateral thoracic and subscapular.

Branches of the Third Part. —The subscapular artery, the largest of all the branches, arises close to the lower border of the subscapularis, and, following this border to the lower angle of the scapula, anastomoses there with the deep branch of the transverse cervical artery. In the upper part of its course it is accompanied by the nerve to latissimus dorsi. In addition to branches to the muscles on the posterior wall, to the serratus anterior, and to the posterior group of axillary glands, it gives off close to its origin a large branch, the circumflex scapular. The circumflex scapular passes backwards through a triangular space bounded above by the subscapularis, below by the teres major, and laterally by the long head of the triceps. It winds round the lateral border of the scapula, grooving the bone, and after passing through the origin of the teres minor, reaches the infraspinous fossa, where it breaks up into numerous branches, which supply the infraspinatus muscle, and which anastomose with branches of the suprascapular and deep branch of transverse cervical. As it passes through the triangular space it furnishes'-an infrascapular branch, which ramifies in the venter of the scapula deeply to the subscapularis, and anastomoses with the ventral branches of the suprascapular and deep branch of transverse cervical. Before passing through the teres minor it gives off a teres branch, which, passing downwards between the teres major and minor to the lower angle of the scapula, anastomoses there with the deep branch of transverse cervical and subscapular arteries. The circumflex scapular sometimes arises directly from the axillary.

The anterior humeral circumflex artery is small, and arises from the outer side of the axillary artery a little below the subscapular artery, and opposite the posterior circumflex. It passes outwards in front of the surgical neck of the humerus deeply to the coraco-brachialis and short head of the biceps. On reaching the bicipital groove it gives off an ascending or bicipital branch, passing upwards in the groove lodging the long head of the biceps, and distributed to the shoulderjoint. Crossing the bicipital groove, it winds round the outer side of the bone, where it anastomoses with the posterior circumflex.

The posterior humeral circumflex artery is large, and arises from the back of the axillary a little below the subscapular. It passes backwards with the circumflex nerve through the quadrilateral space, bounded above by the teres minor (with the subscapularis in front), below by the teres major, medially by the long head of the triceps, and laterally by the surgical neck of the humerus. It . winds round the surgical neck, and has many branches, some of which enter the deep surface of the deltoid. An acromial branch ascending deeply to the deltoid traverses the muscle, and reaches the upper surface of the acromion process, where it anastomoses with the suprascapular and acromial branches of the acromio-thoracic. Other branches become superficial at the hinder edge of the deltoid and supply the skin It anastomoses with the anterior circumflex on the outer side of the humerus, completing an arterial circle embracing the surgical neck, A branch passes downwards between the long and outer heads of the triceps, and anastomoses with the profunda branch of brachial artery

The posterior humeral circumflex artery is subject to certain variations. Ii may arise in common with the subscapular or with the profunda; in the latter case it ascends behind the teres major. It may give off the anterior circumflex, profunda,. or circumflex scapular.



Fig. 267. Axilla viewed from the Front after Removal of Front Wall

Axillary vein and most branches of the artery cut away. To show relations of nerves to artery and of both to the axillary walls.


f Varieties of the Axillary Artery. —The subscapular, circumflex, and profunda ° e rachial may arise by a common trunk. The artery may give origin to a arge: branch, which, extending down to the forearm, may be continuous with e radial, the ulnar, or the common interosseous artery.

The Axillary Vein is mainly the continuation upwards of the basilic resu ^ s f rom the somewhat variable junctions of this vein] an e two venae comites of the brachial artery. As a rule the basilic vein is joined by the medial vena comes at the lower border of the teres major. As the common trunk resulting therefrom is joined at a higher level by the lateral vena comes the axillary vein is somewhat shorter than its companion artery. Its tributaries correspond with the branches of the axillary artery, with the exception of the acromio-thoracic vein, which joins its upper end in common with the cephalic vein.

Axillary Sheath. —The axillary vessels and the brachial plexus of nerves are enclosed in a sheath of loose connective tissue, which is continuous above with the deep cervical fascia, and blends with the deep aspect of the clavi-pectoral fascia.


Fig. 268. — The Brachial Plexus.

Yellow = spinal nerves and their branches; blue=trunks; red=dateral cord; purple = medial cord; grey = posterior cord.


Brachial Plexus (Fig. 268).—The brachial plexus is situated in the lower part of the posterior triangle of the neck, and extends downwards behind the clavicle into the upper part of the axilla. It is a complicated network of nerves, the arrangement of which may be described in four stages—namely: (1) nerve roots, (2) nerve trunks, (3) divisions of the nerve trunks, and (4) nerve cords.

First Stage . — The plexus is derived from the anterior primary divisions of the fifth, sixth, seventh, and eighth cervical, and the first thoracic spinal nerves. Superiorly the plexus is reinforced by a. small descending branch from the fourth cervical, joining the fifth, and interiorly is occasionally reinforced by a branch from the second thoracic, joining the first. The continuation of the anterior primary division of the first thoracic nerve, after giving off the lowermost root of the plexus, is the first intercostal nerve. The roots of the plexus lie between the scalenus anterior muscle in front and the scalenus medius behind.

Second Stage. — The fifth and sixth cervical nerves join at the outer border of the scalenus anterior to form the upper trunk ; the seventh cervical is prolonged independently as the middle trunk ; and the eighth cervical, together with the contribution from the first thoracic, unite between the scalene muscles to form the lower trunk.

Third Stage. — A little above the clavicle each of the three trunks subdivides into an anterior or ventral and a posterior or dorsal division.

Fourth Stage. — The anterior divisions of the upper and middle trunks unite to form the lateral cord of the plexus; the anterior division of the lower trunk is relatively large, and forms the medial cord ; all three posterior divisions (that of the lower trunk being small) unite to form the posterior cord.


As a variety, the anterior division of the middle trunk may subdivide into two branches, one entering the outer cord and the other the inner. The fusions between the nerve roots to form the three trunks may be interpreted as a concentration at the root of the limb of the successive contributions from the spinal nerves destined for the limb. The cleavage into divisions is a primary rearrangement of the nerve fibres into two sets, posterior and anterior, the posterior fibres being gathered together into the posterior cord, which is posterior in position, and whose branches are distributed to the muscles (extensor) and skin disposed on the posterior aspect of the limb, the anterior fibres being prolonged into the lateral and medial cords, which are anterior in position, and their ultimate branches distributed to the muscles (flexor) and skin on the anterior aspect of the limb.

Branches of the Plexus. — The branches may be conveniently classified into two groups: Supraclavicular branches of the nerve roots or of the nerve trunks arising above the level of the clavicle; collateral branches arising from the three nerve cords before their final subdivision; terminal branches, into which the nerve cords ultimately subdivide.

Supraclavicular Branches. — The lowermost root of the phrenic nerve (inconstant) is a branch of the fifth cervical.

The Nerve to the Rhomboids (Posterior Scapular Nerve) (Fig. 269) arises from the back of the fifth cervical close to, or in common with, the highest root of the nerve to serratus anterior; it passes backwards and outwards through the scalenus medius.

The Nerve to Serratus Anterior (Nerve of Bell) arises by three roots from the back of the fifth, sixth, and seventh cervical nerves. The upper two roots pass through the scalenus medius, and appear at its outer edge below the nerve to the rhomboids; the lowest root passes in front of the scalenus medius, and joins the trunk formed by the others j near the first rib. The nerve passing downwards behind the first part of the axillary artery descends into the axilla, where it lies upon ; the axillary surface of the serratus anterior, which it supplies.

Nv. t< Rhomboids


Suprascap. Nv.v.


T Phrenic Nv.


The Nerve to the Subclavius is a small branch arising from the front of the upper trunk, its fibres being derived from the fifth cervical, [t descends in front of the third part of the subclavian artery, and, massing behind the clavicle, enters the deep aspect of the subclavius nuscle. This nerve sometimes communicates with the phrenic nerve.

The Suprascapular Nerve is a large nerve arising from the back

>f the upper trunk, its fibres being derived from the fifth and sixth ervical. It is directed downwards, outwards, and backwards, ying deeply to the trapezius and nferior belly of the omo-hyoid, to

he upper border of the scapula, where it comes into relation with

he suprascapular artery. It is listributed to the supraspinatus, ntraspinatus, and shoulder-joint.

Infraclavicular Branches .—The ateral pectoral, a branch of the ateral cord, derives its fibres from

he fifth, sixth, and seventh cer/ical nerves. It descends in front )f the first part of the axillary irtery, communicates with the nedial pectoral, and, traversing he clavi-pectoral fascia, is finally listributed to the upper part of he pectoralis major.

The medial pectoral nerve, a )ranch of the medial cord, derives ts fibres from the eighth cervical ind first thoracic. It descends )ehind the first part of the axillary artery, and then passes forwards between the artery and the axillary vein. It receives a branch rom the lateral pectoral nerve, with which it forms a loop disposed in ront of the first part of the artery. Its terminal branches enter the leep surface of the pectoralis minor; a few of them pierce that muscle ind enter the deep surface of the pectoralis major.

The three subscapular nerves are branches of the posterior cord, rhe upper subscapular is a small nerve which derives its fibres from he fifth and sixth cervical. It is situated high up on the posterior vail of the axilla, and enters the upper part of the subscapularis. Hie middle, the nerve, to latissimus dorsi derives its fibres chiefly from he seventh cervical, but also from the sixth and eighth. It descends ilong with the subscapular artery to the latissimus dorsi, which it applies. The lower subscapular nerve derives its fibres from the ifth and sixth cervical. Near the lower border of the subscapularis t breaks up into branches, some of which enter the lower part of that nuscle; others end in the teres major.


Fig. 269.— The Supraclavicular Branches of the Brachial Plexus.


Terminal Branches of the Lateral C ord. The musculocutaneous nerve derives its fibres from the fifth, sixth, and seventh cervical, and arises about the level of the pectoralis minor. It lies for a short distance on the outer side of the axillary artery, but passing downwards and outwards it leaves the vessel, and traverses the coraco-brachialis, giving a branch to the muscle before reaching it. The fibres of this branch are derived from the seventh cervical nerve.

This is the usual arrangement in the adult, but in the young subject the nerve to the coraco-brachialis is frequently an independent branch of the lateral cord of the plexus.

The lateral root of the median lies on the outer side of the axillary

artery, and is there joined by the inner root.

Terminal Branches of the Medial Cord .—The medial cutaneous of

arm (lesser internal cutaneous) derives its fibres from the first thoracic. It first lies behind the axillary vein, but descends to its inner side. It communicates with the intercosto-brachial nerve, and is sometimes absent.

The medial cutaneous of forearm (internal cutaneous) derives its fibres from the eighth cervical and first thoracic, and descends partly in front of the axillary artery and partly to its inner side.

The medial root of the median is smaller than the outer, and passes obliquely across in front of the axillary artery to join the outer root a little below the lower border of the pectoralis minor. The trunk of the nerve, which derives its fibres from all the nerves of the plexus, descends on the outer side of the third part of the artery.

The ulnar nerve derives its fibres from the eighth cervical and first thoracic, and is the largest branch of the inner cord, of which it is the continuation. It appears at the lower border of the pectoralis minor, and descends, lying deeply to the inner side of the third part of the axillary artery, between it and the vein.

Terminal Branches of the Posterior Cord .—The circumflex nerve (Fig. 264) derives its fibres from the fifth and sixth cervical nerves. It lies at first behind the axillary artery, resting on the subscapularis, but at the lower border of that muscle it passes backwards through the quadrilateral space in company with the posterior humeral circumflex artery. In this situation (Fig. 273) it supplies an articular branch to the shoulder-joint, and divides into anterior and posterior divisions. The anterior division accompanies the posterior humeral circumflex artery, and divides into a number of branches which enter the deep surface of the anterior part of the deltoid. Some of the branches traverse the muscle and supply the skin over its anterior part. The posterior division gives branches to the posterior part of the deltoid, a branch to the teres minor, and the upper lateral cutaneous nerve of arm, which, winding round the posterior border of the deltoid, are distributed to the skin covering the hinder part of the muscle and the back of the arm. The nerve to the teres minor presents a small swelling, having the appearance of a ganglion, but which is really a fibrous] thickening.


In connection with the distribution of the circumflex nerve, Hilton’s law although not universally applicable, may be here stated: a nerve trunk supplying a given joint also supplies the muscles moving that joint, and the skin covering their insertions. For example, the circumflex nerve supplies the shoulder-ioint the deltoid, and the skin covering its insertion.

The radial (musculo-spiral) nerve (Fig. 270), the largest of all the branches of the plexus, is the continuation of the posterior cord. It ierives its fibres from the last four cervical nerves, and sometimes from the first thoracic as well. It descends behind the third part of the axillary irtery, resting upon the subscapularis, latissimus dorsi, and teres major, [n the axillary space it gives off muscular and cutaneous branches.


die muscular branches supply the long and medial heads of the triceps, hose for the long head being short, and enter the upper part of the luscle; that for the medial head is a long nerve descending in company nth the ulnar nerve, and enters the lower part of the muscle; it is nown as the ulnar collateral nerve (Krause). The posterior cutaneous ranch often arises in common with one of the muscular branches, and asses backwards deeply to the intercosto-brachial nerve to be disnbuted to the skin of the back of the arm, extending downwards early as low as the elbow.

In addition to the branches of the brachial plexus, the skin of the rm is supplied by the intercosto-brachial nerve (Fig. 265), the lateral cutaneous branch of the second intercostal nerve. It escapes fror the second intercostal space between two digitations of the serrate anterior and crosses the axillary space. It usually communicates wit a branch of the lateral cutaneous of the third intercostal nerve, an also communicates with the medial cutaneous of arm and the posteric cutaneous nerve of arm from the radial. It is distributed to the ski covering the inner and back part of the upper part of the arm. A secon intercosto-brachial nerve, derived from a lateral cutaneous branc of the first intercostal nerve, is sometimes present, and when this j the case the medial cutaneous of arm is absent. In some cases th lateral cutaneous of the third intercostal nerve provides an intercostc brachial nerve, which communicates with that from the second, an may largely replace it.

The Axillary Lymphatic Glands are very numerous; they lie em bedded in the loose fatty tissue of the axillary space and are dispose^ in five groups.

The lateral glands lie upon the outer wall of the space, forming chain along the axillary vein. Their afferent vessels are nearly all th superficial and deep lymphatics of the upper limb. Most of thei efferent vessels join the central glands, but some ascend to join th infraclavicular glands or the supraclavicular glands.

The pectoral glands follow the lateral thoracic artery at the lowe border of the pectoralis minor muscle, and under cover of the anterio fold of the axilla. They lie upon the serratus anterior, in the angl between it and the pectoral muscles, and extend from the level of th second to the level of the fifth intercostal space. They receive afferen vessels from the anterior and lateral parts of the thoracic wall, th upper part of the anterior abdominal wall, and the greater part of th mammary gland, especially its lower and outer parts. Their efferen vessels join the central glands, but a few join the infraclavicular glands

The subscapular glands, situated upon the posterior wall of th axilla, follow the lower border of the subscapularis muscle and accom pany the subscapular artery. Their afferent vessels drain the lowe and back part of the neck and the posterior part of the trunk, a fe\ being derived from the lateral abdominal wall. Their efferent lym phatics join the central glands.

The central glands occupy the base of the axilla, and may be re garded as the meeting place of the three preceding groups whosi vessels they receive. Their efferent vessels join the infraclavicula glands.

The infraclavicular glands, which are joined by the efferent vessel of the central glands, are situated in close relation to the upper par of the axillary vein near the upper border of the pectoralis minor.

Serratus Anterior (Fig. 271)— Origin .—The outer surfaces of th< first eight or nine ribs about midway between the angles and costa cartilages by means of fleshy slips or digitations. The first slip arise:

from both the first and second ribs, and from a fibrous arch betweei them.


THE UPPER LIMB


435


Subscapularis


Insertion .—The medial margin, and the ventral surfaces of the ipper and lower angles of the scapular.

Nerve-supply .—The nerve to serratus anterior. The nerve descends m the axillary surface of the muscle.

The muscle is arranged in three parts. The upper part, consisting )f the first digitation, is short, thick, and quadrilateral; it is inserted nto the triangular area >n the ventral aspect of

he upper angle of the capula. The middle part s a thin, expanded sheet, consisting of the second md the third digitations. rhe fibres diverge as they ipproach the scapula, and ire inserted into a linear irea extending for nearly

he whole length of the nedial margin of the

capula. The lower part, consisting of the lower five )r six digitations, is fanshaped, the fibres converging from the ribs to he scapula, where it is nserted into an expanded irea on the ventral aspect )f the lower angle. The


a

h

V

V)


Obliquus

Externus

Abdominis


Fig. 271.—The Serratus Anterior Muscle.


ower four or five digitations interdigitate with those of the obliquus externus abdominis.


The muscle is a curved sheet which, extending backwards from ts origin to its insertion, clings closely to the chest wall, intervening )etween it and the subscapularis (Fig. 263).

Action .—The muscle draws the scapula forwards. The strong ower part, acting upon the lower angle, rotates the bone and elevates he point of the shoulder. In this movement it acts together with he trapezius (p. 399). An important use of the muscle is to fix the scapula, this condition being necessary before the deltoid can elevate he humerus. The muscle serves to keep the lower angle of the capula in contact with the chest wall. When the shoulder is fixed >y other muscles, the lower part of the muscle can raise the ribs, and tot as a muscle of inspiration.


When the serratus anterior muscle is paralyzed (in association with the homboid muscles), the condition known as winged scapula is produced. The ^wer angle and medial border of the scapula are displaced backwards when an uort is made to abduct the arm or to thrust it forwards.






436


A MANUAL OF ANATOMY


The Scapular Region.

The Cutaneous Nerves of the shoulder are derived from the lateral branches of the supra-clavicular nerves and the circumflex. The lateral supra-clavicular branches descend over the acromion process and divide into numerous branches, supplying the skin over the upper part of the deltoid. Some of the branches of the circumflex nerve traversing the deltoid supply the skin over its anterior part; the upper lateral cutaneous nerve of arm, derived from the posterior division, appears at its hinder edge and supplies the skin covering the lower and hinder parts of the muscle.

Deep Fascia. —As it covers the infraspinatus the deep fascia is thick and strong. It is continuous with septa between that muscle and the teres muscles, and between the two teres muscles. At the posterior border of the deltoid it is continuous with the two layers which ensheathe that muscle.

Deltoid (Fig. 272)— Origin .—The anterior border of the outer third of the clavicle; the outer border of the acromion process; and the lower lip of the posterior border of the spine of the scapula.

Insertion .—The deltoid tuberosity on the outer aspect of the shaft of the humerus.

Nerve-supply .—The circumflex nerve (p. 432).

The muscle is very coarsely fasciculated, and is triangular, the base being upwards. The clavicular portion passes downwards and outwards, the acromial downwards, and the spinous downwards and forwards.

Action .—The acromial portion abducts the arm to the position oi nearly a right angle with the trunk; the clavicular portion draws il forwards; and the spinous portion draws it backwards.

The fibres of the acromial part of the muscle are short and obliquely disposed. Attached on either side of four tendinous planes, extending downwards from its origin into the substance of the muscle, the fibres are so disposed as to form a series of feather-like arrangements lying side by side. The fibres^ are attached below on either side of three tendinous planes of insertion, alternating in position with the tendinous planes of origin, and attached below to the humerus.


Ihe anterior border is related to the pectoralis major, which lies deeply to it below, but diverges from it above, the cephalic vein and the deltoid branch of the acromio-thoracic artery lying between the two.. The posterior border is bound down to the deep fascia covering the infraspinatus. Deeply to the muscle are the shoulder-joint, subacromial bursa, coracoid process, coraco-brachialis, biceps, tendons oi insertion of the supraspinatus, infraspinatus, and teres minor; parts of the long and lateral heads of the triceps, teres major, tendon oi insertion of the pectoralis major, circumflex nerve, and posterioi humeral circumflex artery.

The Subacromial Bursa is a large bursa intervening between the' acromion process and deltoid above, and the upper part of the capsulai



THE UPPER LIMB


437


ligament with the tendons inserted into the greater tuberosity of the humerus below.

Supraspinatus^Ongm.—The inner two-thirds of the supraspinous fossa of the scapula, and the deep fascia covering the muscle.

Insertion .—The upper impression on the greater tuberosity of the humerus, its tendon being closely connected with the upper part of the capsular ligament, and with that of the infraspinatus.


Deltoid


Infraspinatus


Teres Minor


-Teres Major


-Triceps, Long Head

'Triceps, Lateral Head


- -Triceps, Medial Head


4 - : f i v



Fig. 272.—Surface View of Muscles of Back of Scapula and Arm.

Nerve-supply .—The suprascapular nerve (p. 431).

The direction of the muscle is outwards and forwards.

Action .—Abducts the arm in association with the deltoid.

Inferior Belly of the Omo-hyoid— Origin .—The upper border of the scapula medial to the suprascapular notch, and the adjacent part of the suprascapular ligament.

Infraspinatus— Origin .—The infraspinous fossa of the scapula for about its inner two-thirds, and the deep fascia covering the muscle.


438


A MANUAL OF ANATOMY


Insertion. —The middle impression on the greater tuberosity c the humerus, its tendon being close by connected with the back par of the capsular ligament, from which it is sometimes separated by bursa. The fibres converge to a tendon which, at first conceale within the substance of the muscle, passes outwards to its insertion.

Nerve-supply. —The suprascapular nerve.

Action. —When the arm is hanging by the side of the trunk th muscle is a. lateral rotator. When the arm is raised the muscle carrie it backwards in association with the deltoid.

The Suprascapular Artery (Fig. 276) is derived from the thyrc cervical trunk, a branch of the first part of the subclavian. It passe transversely outwards behind the clavicle, and reaches the upper borde of the scapula in company with the suprascapular nerve. Havin passed backwards above the suprascapular ligament, the nerve as rule lying below this ligament, it descends into the supraspinous foss deeply to the supraspinatus, to which it gives several branches Finally, it passes downwards behind the neck of the scapula throug] the spino-glenoid notch, deeply to the spino-glenoid ligament, inf the infraspinous fossa, where it supplies the infraspinatus, deeply t which it lies, and anastomoses with the circumflex scapular and dee] branch of transverse cervical.

Branches. — Muscular, in the neck, to the sterno-mastoid an< subclavius; suprasternal, passes downward in front of the sterno clavicular joint, and supplies the skin over the manubrium; nutrient to the clavicle; acromial, traverses the trapezius to reach the uppe surface of the acromion process, where it anastomoses with, branche of the acromio-thoracic and posterior circumflex; articular, to th acromio-clavicular and shoulder-joints; anterior, given off as it passe backwards over the suprascapular ligament, and anastomosing in th subscapular fossa with the circumflex scapular and deep branch 0 transverse cervical; supraspinous and infraspinous, distributed to th muscles on the back of the scapula.

The Suprascapular Nerve passes backwards below the supra scapular ligament into the supraspinous fossa, where it gives branche to the supraspinatus and articular branches to the acromio-clavicula and shoulder-joints. It accompanies the artery through the spino glenoid notch, lying deeply to the spino-glenoid ligament, to th infraspinous fossa, where it ends in branches to the infraspinatus.

Teres Minor (Fig. 273)— Origin. —A long narrow area on the dorsun of the scapula close to the lateral border, and the septa between it an( the infraspinatus and the teres major respectively.

Insertion. —The lower impression on the greater tuberosity of th humerus, and the surgical neck of the bone for a short distance below

its tendon being closely connected with the back part of the capsula] ligament.

Nerve-supply. —A branch of the circumflex nerve (p. 432).

The direction of the muscle is outwards and slightly upwards and forwards.


THE UPPER LIMB - 439

Action .—When the arm is abducted it is a lateral rotator; it also assists in depressing the arm.

Teres Major (Fig. 273)— Origin .—From an oval impression on the dorsupi of the scapula near its lower angle, and from the lower third of the lateral border; also from the septa between it and the teres minor and infraspinatus respectively.

Insertion .—The medial lip of the bicipital groove of the humerus for about 2 inches.


Supraspinatus


The deltoid, supraspinatus, and infraspinatus muscles have been partially removed. The boundaries of the quadrilateral and two triangular spaces as they appear from behind.


Nerve-supply .—The lower subscapular nerve (p. 43 1 )*

The direction of the muscle is obliquely upwards, outwards, and forwards.

Action .—Adducts the arm, and when the arm is abducted acts as a medial rotator.

The latissimus dorsi winds round the lower border of the muscle, and is finally placed in front of it. The two tendons are at first closely connected by their lower borders, but close to their insertions are







440


A MANUAL OF ANATOMY


separated by a bursa. A bursa between the teres major and the humerus is sometimes present.

Subscapularis (Fig. 270)— Origin .—The anterior surface of the scapula, with the exception of the neck, and the areas giving attachment to the serratus anterior. The origin of the muscle fibres is partly from a series of tendinous planes embedded in the substance of the muscle, and attached to the ridges on the anterior surface of the


- Supraspinatus


Infraspinatus


Teres Minor


Teres Major

Teres Branch of Circumflex*

Scapular Artery Circumflex Scapular Artery in Triangular Space Nerve to Teres Minor, with Gangliform-' Enlargement


“ - Posterior Humeral Circumflex Artery and Circumflex Nerve in Quadrangular Space


- Pectoralis Major


Long Head of Triceps_


Deltoid


Fig. 274* Dissection of the Scapular and Upper Brachial Regions

from Behind.

The with°it anH b t e hTf tUrned , d0W ^ Carryin 8 the circumflex nerve and vessi content’s, are shown™ 5 quadrangular muscular spaces, with th<

between theridgel m6anS ° f muscle sh P s attached to the depressioi

descendf dow^ The d leS / er tuberosit y of the humerus, from which descends downwards for some little distance on to the neck of tf

mrvei'lp'Ts ^ 7116 UPP6r ' ^ Partly by the lower ' subsca P uI{

















THE UPPER LIMB


441


The direction of the muscle is mainly upwards and outwards.

Action. —Rotates the arm inwards, and when it is raised draws it forwards and downwards.

The tendon of the muscle is closely blended with the front of the capsular ligament. Between it and the neck of the scapula is a bursa, which is continuous with the synovial membrane of the shoulder-joint through a deficiency in the capsule.

Triangular and Quadrilateral Spaces (Fig. 275).—As the long head of the triceps descends obliquely downwards and outwards from the infraglenoid tubercle of the scapula to the back of the shaft of the humerus, it lies behind the teres major and in front of the teres minor, these two muscles diverging from one another as they pass outwards to the humerus. The long head of the triceps with the two teres muscles and the shaft of the humerus help to form the boundaries of a quadrilateral and two triangular spaces.

The Quadrilateral Space is bounded above by the teres minor, together with the subscapularis lying in front of it, the lower edges


^ IG * 2 75 -—Diagrams to show Formation of Triangular and

Quadrilateral Spaces.

of the two muscles being at the same level; below by the teres major, m front of which is the tendon of the latissimus dorsi; laterally by the neck of the humerus; and medially by the long head of the triceps. This space is occupied by the circumflex nerve and posterior humeral circumflex artery.

The Upper Triangular Space, bounded above by the teres minor and subscapularis, below by the teres major, and laterally by the long head of the triceps, contains the commencement of the circumflex scapular artery.

The Lower Triangular Space, bounded above by the teres major and the tendon of the latissimus dorsi, medially by the long head of the triceps, and laterally by the shaft of the humerus, transmits the radial nerve and the profunda artery to the back of the arm.

Scapular Anastomosis (Fig. 276).—The anastomoses of arteries about the scapula are divided into two sets—scapular proper and acromial.

Scapular Anastomoses Proper. —The arteries taking part in these anastomoses are the suprascapular and deep branch of transverse








44 2


A MANUAL OF ANATOMY


cervical, deriving their blood from the subclavian; and the circumflex scapular branch of the subscapular, derived from the third part of th< axillary. The suprascapular is a branch of the thyro-cervical trunl from the first part of the subclavian; the transverse is also a branch o: the thyro-cervical trunk. The suprascapular and deep branch oi transverse cervical are distributed to the supraspinous and infra Acromial Branch Acromial Rete


spinous fossae and anterior surface. The circumflex scapular ramifies m e miraspmous fossa and anterior surface. In the supraspinous ossa e suprascapular anastomoses with the deep branch of transverse cervica . n the infraspinous fossa the suprascapular, the circumflex scapu ar, and the deep branch of transverse cervical anastomose oge er. n the anterior surface of the scapular the ventral branches o e suprascapulai and deep branch of transverse cervical anastomose









THE UPPER LIMB


443


with the ventral branch of the circumflex scapular. At the lower angle of the bone the deep branch of transverse cervical anastomoses with the descending or teres branch of the circumflex scapular.

Acromial Anastomosis. —The arteries taking part in the acromial anastomosis or rete on the upper surface of the acromion process are the acromial branch of the suprascapular, branches of the acromiothoracic artery, and twigs from deep branch of transverse cervical.

The scapular anastomoses are of importance in providing collateral channels for the blood after ligature of the third part of the subclavian artery.


The Articulations of the Clavicle.

Sterno-clavicular Joint (Fig. 277).—The articular surfaces are the inner end of the clavicle and the clavicular notch on the upper border of the manubrium sterni. The articular surface of the clavicle is larger than the sternal, and the two are separated by an interarticular disc.


Interclavicular

Anterior Sterno-clavicular Ligament Ligament Articular Disc


The left anterior sterno-clavicular ligament has been removed.

The joint is surrounded by a complete capsule, weak above and below, but strong in front and behind, where it provides the anterior and posterior sterno-clavicular ligaments. In addition, there are the interclavicular and costo-clavicular ligaments.

The anterior sterno-clavicular ligament is broad, and its fibres extend obliquely downwards and inwards from the front of the clavicle to the front of the manubrium. The sternal head of origin of the sternomastoid lies in front of it. The posterior sterno-clavicular ligament resembles the anterior, and is similarly disposed behind the joint. The sterno-hyoid muscle arises in part from it. The interclavicular ligament is a well-marked, curved bundle of fibres, attached at either side to the upper and back part of the inner end of the clavicle. As it extends between the two bones it curves downwards to be attached to the suprasternal notch on the upper border of the manubrium. The costo-clavicular or rhomboid ligament is a strong, quadrilateral band of fibres extending from the upper surface of the first costal cartilage to the rhomboid line on the under surface of the clavicle; its direction is upwards, backwards, and outwards.



444


A MANUAL OF ANATOMY


The articular disc is a nearly circular, flattened plate, thinner at the centre and lower part than elsewhere. It is attached above to the upper and back part of the inner end of the clavicle, and below to the inner end of the first costal cartilage, where it inclines slightly outwards to form with the first costal cartilage a socket for the inferior aspect of the inner end of the clavicle. Circumferentially it is adherent to the capsular ligament. The plate sometimes presents a central deficiency.

The joint has two synovial cavities, one on either side of the articular disc. When the latter is perforated these are continuous with each other.

Nerve-supply. —The medial supraclavicular.


.—• Glenoid Ligament


Movements. —These take place in upward, downward, forward, and backward directions. A combination of these movements or circumduction can also occur. In the upward and downward movements the clavicle moves on the articular disc, and the forward and backward movements take place between the articular disc and the manubrium. Upward displacement of the inner end of the clavicle is limited by the costo-clavicular ligament and the articular disc.

Acromio-clavicular Joint. —The articular surfaces are the outer end of the clavicle and the facet on the acromion process. These surfaces are occasionally partially separated by an incomplete articular disc. The joint is surrounded by a capsular ligament, thickened above and below, forming the superior and inferior ligaments.

The acromio-clavicular ligament extends between the corresponding margins of the bones, the former being strengthened by aponeurotic

fibres from the trapezius and deltoid. The articular disc, when present, is limited to the upper part

of the joint, where it is . Coracoid Ligament atta ched to the ligament.

Occasionally it is complete, and subdivides the joint into two synovial compartments.

The coraco-clavicular ligament, an accessory ligament to the joint, connects the clavicle with the coracoid process, and is composed of two parts —conoid and trapezoid. The conoid ligament, medial and posterior in position, is attached below by . , , its apex to an impression

at the back part of the antero-medial border of the coracoid process, and above by its base to the conoid tubercle of the clavicle, its direction being upwards and backwards. The trapezoid ligament, lateral and


- Biceps


.Glenoid Labrum


Fig. 278. The Right Glenoid Cavity and the Adjacent Ligaments.






THE UPPER LIMB


445


anterior in position, is somewhat quadrilateral. It is attached below to the trapezoid ridge on the back part of the upper surface of the coracoid process, and above to the trapezoid ridge on the under surface of the clavicle, its direction being upwards, backwards, and outwards. Between the two ligaments there is a slight interval, which may be occupied by a bursa.

Nerve-supply. —The lateral supraclavicular.

Movements. —The movements at this joint are very limited, and consist chiefly of gliding in upward and downward, and forward and backward directions.


The Ligaments of the Scapula.


The suprascapular ligament (Fig. 273) extends from the upper border of the scapula, medial to the suprascapular notch, to the root of the coracoid process. It is thin and flat, bridges across the notch, and converts it into a foramen. It gives origin to some fibres of the inferior belly of the omo-hyoid; the suprascapular nerve passes below it, the suprascapular artery above it.

This ligament is sometimes replaced by bone.

The coraco-acromial ligament is triangular, and is attached by its apex to the tip of the acromion process, by its base to the posterolateral border of the coracoid process. Its superior surface is covered by the deltoid, and the inferior surface overhangs the shoulderjoint, the subacromial bursa intervening. The acromion process, coraco-acromial ligament, and coracoid process

form the coraco-acro- Fig. 279. —Coraco-acromial (CA) Ligament, Coramial arch, which lodges co-humeral (CH), and Capsule of Shoulder. the head of the hu- C> conoid ligament ; SS, suprascapular ligament ; merus when the arm is s ^ or ^ head of biceps; F, foramen for long head

abducted. The arch ° f blceps '

therefore forms an auxiliary socket for the head of the bone.

The spino-glenoid ligament consists of a few fibres extending


44 6


A MANUAL OF ANATOMY


from the outer border of the spine to the adjacent part of the margin of the glenoid cavity. It arches over the suprascapular artery and nerve as they pass through the spino-glenoid notch on their way to the infraspinous fossa.

Movements of the Scapula.—These movements^take place at the acromio-clavicular joint, and are associated with Inovements of the clavicle. They are of two kinds—namely, gliding and rotation.

Gliding Movements.—These take place upwards, downwards, outwards or forwards, and inwards or backwards. As they occur the scapula moves over the dorsal wall of the thorax in such a manner as to describe the arc of a circle. The centre of this circle corresponds to the sterno-clavicular joint, and the clavicle represents a ray of the circle. In the inward or backward movement the medial border of the scapula approaches the vertebral column; in the outward or forward movement it retreats from the vertebral column.

Rotatory Movements.—Rotation takes place inwards and outwards. During medial rotation the acromion is elevated , the superior angle is depressed, and the inferior angle moves slightly outwards. In medial rotation the conoid ligament is tightened. During lateral rotation the superior angle is elevated, the acromion is depressed, and the inferior angle moves slightly inwards. In lateral rotation the trapezoid ligament is tightened.

Chief Muscles concerned in the Movements.—Elevation of Entire Scapula: Cervical part of the trapezius, and the levator scapulae. Depression of Entire Scapula : The lower fibres of the trapezius, and the pectoralis minor. Outward or Forward Movement of Entire Scapula: The serratus anterior. Inward or Backward Movement of the Entire Scapula : The middle and lower parts of the trapezius, and the rhomboid muscles.

Special Movements.—Elevation of Acromion: Cervical part of the trapezius. Elevation of Superior Angle : Levator scapulae, aided by the rhomboid muscles.

The inferior angle of the scapula is kept in contact with the dorsal wall of the thorax by the upper horizontal fibres of the latissimus dorsi muscle, which pass over its dorsal aspect.

The medial border of the scapula is kept in contact with the dorsal wall of the thorax by the serratus anterior and rhomboid muscles.


The Arm.

Landmarks.—The front of the arm presents a well-marked elongated prominence, which reaches from the anterior fold of the axilla to neai the elbow, and is due to the biceps. Medial to it in the upper part of the arm is another smaller swelling caused by the coracobrachialis. On either side of the bicipital prominence is a groove, that on the outer side indicating the position of the cephalic vein, and that on the inner side the position of the basilic vein, brachial artery, and median nerve. Lateral to the bicipital prominence, for a short


THE UPPER LIMB


e\


■Til


MCA


MCA



ri_n


447

distance above the elbow, is the prominence formed by the brachioradialis and extensor carpi radialis longus. At the elbow the medial md lateral epicondyles of the humerus and the olecranon process )f the ulna are to be noted. The medial epicondyle forms a very distinct projection, having an inclination backwards; behind it, close

o the olecranon, is the ulnar nerve. The lateral epicondyle is rot so well marked, but may be felt in semiflexion of the joint. The decranon process can easily be felt at the back of the elbow. When

he joint is extended, the summit of the olecranon and the two epi:ondyles are all in line with one another. When the arm and forearm ire at right angles to one another, the summit of the olecranon is below a line connecting the epi:ondyles. In extreme flexion of the dbow the summit of the olecranon s in front of a line connecting the epicondyles. The posterior surface if the olecranon is covered by a mbcutaneous bursa. When the joint s extended, the head of the radius

an be felt at the bottom of a depression situated at the outer and lack part, immediately below the ateral epicondyle. It is most readily telt when the forearm is alternately Dronated and supinated. In front )f the elbow there is a slight hollow ndicating the position of the ante:ubital fossa, and in this region the nedian basilic and median cephalic veins may be visible through the

kin. On the back of the forearm he posterior subcutaneous border )f the ulna can readily be felt. It extends from the apex of the trimgular surface on the back of the decranon process downwards and nwards to the styloid process at he lower end of the ulna, occupying the back of the inner side of he waist. The styloid process of the radius projecting downwards o a lower level than that of the ulna can easily be felt on the outer ade of the lower end of the bone. About the middle of the back of

he lower end of the radius is the dorsal tubercle, which bounds laterally he groove for the tendon of the extensor pollicis longus.

The Olecranon Bursa is situated subcutaneously on the posterior triangular surface at the back of the olecranon process of the llna.

Cutaneous Nerves. —The intercosto-brachial nerve, having crossed he axillary space, supplies the skin of the inner and back part of the


MC


MC


M


Fig. 280.—Diagrams of Cutaneous Nerves of Upper Limb, Front and Back.










448


A MANUAL OF ANATOMY


upper part of the arm. It may be accompanied by a twig from th lateral cutaneous branch of the third intercostal nerve.

The medial cutaneous nerve of arm (lesser internal cutaneous) i distributed to the skin of the inner side of the arm, as low as the interw between the medial epicondyle and olecranon.

The medial cutaneous nerve of forearm (internal cutaneous) sends on or more branches, which, traversing the deep fascia close to the axilk are distributed to the skin covering the biceps. The nerve itself passe through the deep fascia a little below the centre of the arm, and divide into anterior and posterior branches. The anterior branch descend behind, sometimes in front, of the median basilic vein, giving one o two twigs supplying the neighbouring skin, and finally descending int< the forearm is distributed to the skin on the anterior aspect of its inne side. The posterior branch passes downwards and inwards on th inner side of the basilic vein. Extending downwards over the media epicondyle, it finally passes backwards to supply the skin over th back of the inner side of the forearm.

The posterior cutaneous nerve of arm (internal cutaneous of musculo spiral) is distributed to the skin on the back of the arm, usually as lov as the olecranon.

The posterior cutaneous nerves of forearm (external cutaneous o musculo-spiral) are two in number—upper and lower. They leav< the main trunk towards the lower end of the spiral groove, just befon the nerve passes through the lateral intermuscular septum. The uppe> branch is small, and descends with the cephalic vein to the front of thf elbow; it supplies the skin on the outer side of the lower part of the arm. The lower branch is much larger and descends behind thelatera epicondyle into the forearm, where it is distributed to the skin or the posterior aspect as low as the wrist.

The lateral cutaneous nerve of forearm (external cutaneous) pierces the deep fascia on the outer side of the biceps a little above the elbow, It descends behind the median cephalic vein, giving one or two twigs to the skin in the neighbourhood, and divides into two branches. One supplies the skin on the outer side of the front of the forearm, and the other gives branches to the skin on the back of the forearm.

The cutaneous branch of the ulnar, an inconstant branch, arises about the middle of the forearm, pierces the deep fascia, and has a

muted distribution to the skin on the front of the lower part of the forearm.


Superficial Veins (Fig. 281).—There are four principal superficial uhrar m ^ orearm: me dian, radial, anterior ulnar, and posterior


he median vein is formed by the union of a few radicles which origma e m the venous plexus in front of the wrist, and its course is upwards m front of the forearm. As it ascends it is joined by severa veins, and often receives a large tributary from the back of e 1m . It is in free communication with the radial and anterior uinar veins. On arriving at the hollow in front of the elbow it re


THE UPPER LIMB


449


Fig. 281.—The Superficial Veins of the Upper Limb

(Anterior View).


29







450


A MANUAL OF ANATOMY


ceives a short but large tributary, the deep median vein, which esta lishes a communication between it and the deep veins. It divid into the median cephalic and median basilic veins, which diver from each other as they ascend like the capital letter V. The medii cephalic vein, the smaller of the two, passes upwards and outwar in the interval between the biceps and brachio-radialis; the muscul cutaneous nerve lies deeply to it, but a few twigs of the nerve are supe ficial to it. A little above the lateral epicondyle it is joined by ti radial vein, the resulting trunk being the cephalic vein. The medii


Fig. 282.—To show Variations in Superficial Veins of Front of Arj

The first figure gives the commonest variety: C-C, cephalic vein; B-B, basil] vein; MC, median cubital joining these two: accessory minor veins ma include MA, median antebrachial, and AC, accessory cephalic. The r< maining figures show two only out of a very large number of possible varietie: The deep median ’ joins the superficial veins at the bend of the elbow wit the venae comitantes of the deep arteries.

basilic vein, the larger of the two, passes inwards and upwards, crossin] the bicipital aponeurosis, which separates it from the brachial arter and the median nerve; the anterior branch of the medial cutaneou nerve of forearm descends behind or in front of it. Just a little wa; above the medial epicondyle it is joined by the anterior and posterio u nar veins, either separately or as a common trunk; the resulting vessel is the basilic vein.

, +? ie , rac ^ a ^ ve * n > usually continuous below with a vein on the bac o he thumb, drains the outer part of the plexus on the back of th












THE UPPER LIMB


45i


md, and ascends on the back of the outer side of the forearm. Windg round to the front of the limb, it joins the median cephalic vein little way above the lateral epicondyle.

The anterior ulnar vein commences on the inner aspect of the ont of the wrist, and ascends in front of the inner side of the fore•m, to end either in the median basilic or by joining the posterior nar vein.

The posterior ulnar vein is large, and commences in the inner irt of the plexus on the back of the hand; it ascends on the back

the inner side of the forearm, and joins the median basilic, either idependently or in common with the anterior ulnar vein.

The principal superficial veins of the arm are the cephalic and le basilic.

The cephalic vein is formed by the union of the median cephalic id the radial a little distance above the lateral epicondyle. It >cends, lying at first in the groove at the outer border of the biceps, id at a higher level between the pectoralis major and deltoid. Finally,

crosses the first part of the axillary artery, and, traversing the avi-pectoral fascia, joins the axillary vein above the pectoralis minor.

The basilic vein is formed by the union of the median basilic with le anterior ulnar and posterior ulnar veins just above the medial Dicondyle. It ascends in the groove on the inner border of the iceps, lying to the inner side of the brachial artery. In the lower art of the arm it is superficial, but passing through the deep fascia bout the middle of the arm, it becomes continuous above with the sillary vein (p. 428). In relation with the basilic vein, just above le medial epicondyle, are one or two lymphatic glands.

Front and Inner Aspects of the Arm.

Deep Fascia. —The deep fascia provides a complete investment )r the arm, its fibres being principally disposed transversely, but thers run more or less longitudinally. It is continuous above with le axillary fascia and the fascial investments of the pectoralis major ad deltoid, the tendons of which give expansions to it. It is thin yer the biceps, and somewhat thicker over the triceps, but it becomes serially strong in the region of the elbow, where it is attached to the picondyles of the humerus and olecranon process of the ulna. In ont of the elbow it receives a considerable accession of fibres from le bicipital aponeurosis. At about the middle of the arm, on its inner spect, it presents an opening for the passage of the basilic vein. The eep fascia is connected with the lower part of the humerus on either de by two^ intermuscular septa. The lateral septum is attached to ie lateral epicondyle and the lateral supracondylar ridge. Arching "ross the spiral groove, containing the radial nerve and profunda Tery, it extends upwards to the insertion of the deltoid, with which it is )nnected. It gives origin posteriorly to the medial head of the iceps, and above to the lateral head of the muscle. Anteriorly,


452


A MANUAL OF ANATOMY


from above downwards, it gives origin to a small part of brachial to the brachio-radialis, and to the extensor carpi radialis longi The posterior terminal branch of the profunda artery descends behii it. The medial septum is stronger than the lateral and is attach to the medial epicondyle and the medial supracondylar ridge as hij as the insertion of the coraco-brachialis. It gives origin anterior to brachialis, and posteriorly to the medial head of the triceps, is pierced at its upper part from before backwards by the ulnar ner and ulnar collateral artery, and a little above the elbow by t] posterior branch of the supratrochlear artery. Connected with t' medial septum there is a fibrous band, known as the medial brachi ligament (Struthers), which extends from the humerus below t] tendon of insertion of the teres major to the medial epicondy] By means of the humerus and the two intermuscular septa the low part of the arm is subdivided into two compartments: an anteri< containing the flexor muscles, and a posterior containing the extens muscles.

The Supratrochlear Lymphatic Glands. — These glands, usual two in number, are situated about ij inches above the medial ej condyle of the humerus. They lie in the subcutaneous tissue close proximity to the commencement of the basilic vein. The afferent vessels are derived from the inner three fingers, the inn part of the palm, and the ulnar side of the forearm. Their effere\ vessels ascend with the basilic vein, and join the deep lymphatl accompanying the brachial artery; they terminate in the later axillary glands.

The Antecubital Lymphatic Glands are very inconstant. Whe present, they are found in the subcutaneous tissue at the bend of tl elbow. They receive afferent vessels from the middle of the palm an the front of the forearm. Their efferent vessels accompany the basil vein, and end in the lateral axillary glands.

Coraco-brachialis — Origin. —The tip of the coracoid process of tl scapula and the inner aspect of the tendon of the short head of tl biceps.

Insertion. —An impression on the inner aspect of the shaft of tl humerus about the middle of the bone. Some of the upper fibres ai inserted into a fibrous band, which arches across the tendons of tl latissimus dorsi and teres major, and is attached above to the humeri immediately below the lesser tuberosity.

Nerve-supply. A branch of the musculo-cutaneous, contains fibres from the seventh cervical nerve.

the muscle is directed downwards, outwards, and slightly bacll wards. J

Action. Adducts the arm and flexes the shoulder-joint. j

Ihe muscle is traversed by the musculo-cutaneous nerve.

Biceps Brachii (Fig. 284)— Origin. —The short head arises from tl ip of the coracoid process of the scapula in common with the corac< rac lalis, the long head arises by tendon from the supraglenoid tuberc



THE UPPER LIMB


453



Brachio Rad.'


Radial Extensors —&


the scapula, where it is continuous on either side with the labrum enoidale. The tendon lies within the limits of the capsular ligament

the shoulder-joint. Insertion .—The posterior rough portion of the tuberosity of the idius, being separated from the anterior smooth portion by a bursa; id into the deep fascia covering the flexor muscles arising from the ledial epicondyle of the humerus by means of the bicipital aponeurosis.

The short head arises y a short tendon, the

ndon of the long head clWV sing about 4 inches in ngth. This latter tendon xhes over the head of le humerus, and leaves le joint by entering the icipital groove, which is mverted into a canal by t

le transverse humeral ^anient. Within the )int it is invested by a iflexion of the synovial Lembrane, which is promged downwards for a

lort distance into the m m v

icipital groove, where it rovides a synovial sheath >r the tendon. After aving the bicipital groove le tendon is replaced by conical bundle of fleshy bres, and these, joining le fibres derived from le short head about the tiddle of the arm, give se to an elongated, oval, eshy belly. At the level i the epicondyles of the umerus the belly gives Fig. 283.lace to the strong tenon of insertion, which,

3 it sinks backwards into the antecubital space to reach its insertion,

• twisted upon itself in such a manner that its outer edge comes to >ok forwards. From the inner side of the upper part of this tendon strong band of fibres is prolonged downwards and inwards, and lends with the deep fascia covering the flexor muscles arising from oe medial epicondyle. This band, called the bicipital aponeurosis, ridges across the brachial artery and median nerve; the median basilic ein and the medial cutaneous nerve of forearm lie superficially to it.


Coraco Brachialis


Scapular Head of Triceps


Medial Head of Triceps

— Biceps

- Brachialis

- Pronator Teres Sup. Head — Bicipital Apon.


__JL F. Carpi Rad.

Palmaris Longus fJjL F. Dig. Sublimis

-F. Carpi Ulnaris


Abd. Poll. Long. — Pronator Quad. —


3


-Front View of Muscles of Free ’ Upper Limb.





454


A MANUAL OF ANATOMY


Nerve-supply. —Branches of the musculo-cutaneous, contain! fibres from the fifth and sixth cervical nerves.

Action .—Flexes the elbow-joint, and is a powerful supinator of t forearm; it is also a flexor of the shoulder-joint.

Medial to the upper part of the muscle is the coraco-brachial and to its lower part the brachial artery and median nerve. To

outer side is the cepha


Coraco-Brach. M.


- Prof. A.


--Nfc-Triceps, Long Hd.


vein. As a rule, it is late: to the brachial artery, t when well developed may in front of it for some d tance.


The biceps sometimes ha: third head, which usually ari from the inner side of the 1 merus at or near the insertion the coraco-brachialis.


Triceps, Med. Hd.


Ulnar Nv.


Median Nv.


Ulnar Collat. Art.


Supra-troc. Art.


— --Brach. M.


Brachialis — Origin .—T lower half of the front the humerus; the front the medial intermuscul septum for its whole exter and the front of the latei intermuscular septum for short distance above.

Superiorly the area attachment of the mus( bifurcates to embrace t lower part of the insertii of the deltoid, the outer si occupying the floor of t' spiral groove.

Insertion. — The rouj

triangular surface below t coronoid process of the uln Nerve-supply .—Branch of the musculo - cutaneo nerve, containing fibres fro the fifth and sixth cervic nerves, and a twig from t] radial nerve.

Action .—A flexor of tl elbow-joint.

Brachial Artery (Fig. 284).—The brachial artery is the continuatic of the axillary, and extends from the lower border of the teres maj< to a point just below the bend of the elbow, where it divides opposi the upper part of the neck of the radius into the radial and uln; arteries. It is at first medial to the humerus, but gradually incline


' “ Bicip. Apon.


- - Ulnar A.


"Radial A.


Fi g. 284.— The Brachial Artery from in Front, illustrating its Main Branches and More Important Relations.











THE UPPER LIMB


455


o the front of the bone, and at the elbow is situated midway between he two epicondyles. The course of the vessel is indicated by a line Irawn from the inner border of the coraco-brachialis to a point midway >etween the epicondyles of the bone. The artery is accompanied by wo venae comites, which lie one on either side, are connected together >y numerous transverse communications which lie both in front of ,nd behind the artery, and thus communicate with each other across he vessel at frequent intervals. It is for the most part superficial, )eing only slightly overlapped by the coraco-brachialis and biceps. At he bend of the elbow, however, it sinks deeply under cover of the >icipital aponeurosis, and lies in the antecubital space.

Relations — Superficial. —Skin, superficial and deep fasciae, the aedian nerve towards the lower part of the arm, bicipital aponeurosis if the biceps, and, superficial to this, the median basilic vein. Deep .— 'he long head of the triceps, with the intervention of the radial nerve nd profunda artery, medial head of the triceps, insertion of the coraco>rachialis, and brachialis. Lateral. —The coraco-brachialis and biceps, >oth of which slightly overlap the vessel, lateral vena comes, and the nedian nerve in the upper part of the arm. Medial. —The medial vena omes, medial cutaneous nerve of forearm (which may be slightly in ront of the vessel), the ulnar nerve in its upper part, and the median ierve in its lower part, and the basilic vein. The nerve most intimately elated to the artery is the median, which, lying on its outer side in the ipper part of the arm, crosses in front of it, and for some little distance hove the elbow lies on its inner side.

Branches.— A series of small irregular branches are distributed to he muscles and skin on the front of the arm. The named branches rise from the inner and back part of the trunk.

The profunda artery (Fig. 285) is a large vessel arising from the back f the brachial near its commencement. It passes downwards and ackwards with the radial nerve between the long and medial heads f the triceps, and winds round to the back of the shaft of the humerus, yfing with the nerve in the spiral groove between the lateral and medial eads of the muscle. Towards the lower end of the groove it divides ito two terminal branches—anterior and posterior. The anterior ranch accompanies the radial nerve through the lateral intermuscular sptum, and descends between the brachio-radialis and brachialis to nastomose with the radial recurrent artery. The posterior branch escends behind the lateral intermuscular septum, and anastomoses ehind the lateral epicondyle with the posterior interosseous recurrent, nd across the back of the humerus above the olecranon fossa with the jpratrochlear. In addition to the two terminal branches the promda gives off muscular branches to the triceps; an ascending branch , assing upwards between the long and lateral heads of the triceps to nastomose with a branch of the posterior humeral circumflex; and a utrient branch , which enters a foramen on the back of the humerus.

The profunda may arise from the third part of the axillary, or may arise in )mmon with the posterior humeral.


456


A MANUAL OF ANATOMY


The ulnar collateral artery arises from the brachial about the mi< of the arm. It accompanies the ulnar nerve, passing through

medial intermuscular septum,


Acromial Rete


l-.A-l-- Profunda


Ulnar Collat.


Supra-Scapular


•lAcromio Thoracic


Post. Circumflex Ant. Circumflex


...Subscapular --Circumflex Scapular


- Supra-Troc.


"Ant. Ulnar Rec.


p — Post. Ulnar Rec.


' Radial Rec.


Post. Inteross. Rec.


descends with the nerve on medial head of the triceps to back of the medial epicondyle, wl it anastomoses with the suj trochlear and posterior ulnar re< rent arteries. It supplies musci branches to the triceps.

The nutrient artery arises fi the brachial opposite the lo border of the insertion of coraco-brachialis, or it may cc off from the ulnar collateral, passes downwards and enters nutrient foramen of the bone.

The supra-trochlear artery ar: about 2 inches above the elb< It passes inwards on brachialis, ; divides into two branches-—a sn anterior and a larger posterior. 1 anterior branch descends in front the medial epicondyle, and anas moses with the anterior ulnar rec rent artery. The posterior brai passes through the medial int muscular septum, and, passing o wards on the back of the humei above the olecranon fossa lyi deeply to the triceps, it comple an arterial arch with the poster branch of the profunda artery, sends a branch to the back of t medial epicondyle, where it an; tomoses with the ulnar collateral a: posterior ulnar recurrent arteries.


Varieties. —i. The brachial artery n divide at a higher level than usual, most cases the abnormally early brai is the radial; more rarely it is the uln and in these cases the interosseous tru arises from the radial; still- more ran the premature branch is the interossec trunk, or a large vas aberrans. 1 is most frpnn^^-i • ,1 . ^ eve * a t which a high division takes pk

third and rar^i ^PPf r ttu r( I of the arm, less frequently in the lov

usuallv Ue S ? ^ fi? dle third - When two arteries are present, tt

a vasaberran front ° f .? e median nerve and the other behind it. Wh 1 present, it usually arises from the upper part of the brach


. jr*ct • G - 285.-Jo ILLUSTRATE THE RE LATIONS of the Brachial Artery and its Branches to the Skeleton, AND THEIR PROXIMAL AND

Distal Anastomoses.












THE UPPER LIMB


457

tery, lies in front of the median nerve, and terminates below by joining, most mmonly, the radial artery.

2. In rare cases the brachial artery divides high up into two vessels of equal ie, which become reunited into one trunk a little above the elbow.

3. When a supracondylar process is present the brachial artery, together ith the median nerve, may descend behind it, and then pass forwards to the Dnt of the elbow below it. This course resembles that of the artery in the elides, in which a supracondylar foramen is normally present.



Medial Cutaneous Nerve of Forearm

Basilic Vein -

Median N erve_ 1 .I*..

Brachial Artery and Venae Comites


Posterior Branch of Medial Cutaneous Nerve of Forearm

Basilic Vein

Anterior Branch of Medial Cutaneous Nerve of Forearm Median Cubital Vein

Bicipital Aponeurosis -

Ulnar Artery and Venae Comites


Anterior Ulnar Vein

Pronator Teres—-—


-Brachialis


__Biceps


_Cephalic Vein


_Musculo-cutaneous

Nerve


Cephalic Vein


. Radial Vein


Deep Median Vein

Radial Recurrent Artery

Radial Artery and Venae Comites


Cephalic Vein Branchio-radialis


Fig. 286. —Superficial Dissection of the Front of the Left Elbow.


Collateral Circulation. —When the upper part of the brachial artery > tied, the circulation is maintained by the profunda artery, which nastomoses below with the radial recurrent, the posterior interosseous scurrent, and the supratrochlear. When the artery is tied in the sgion of the elbow, the ulnar collateral and supratrochlear, by anastolosing with the anterior and posterior ulnar recurrent, provide addiional channels.

The medial cutaneous nerve of forearm and the medial cutaneous ierve of arm lie to the inner side of the brachial artery, the former






























45« 


A MANUAL OF ANATOMY


slightly overlapping it in front. In the upper part of the arm th median nerve lies on the outer side of the artery, but as it descends i crosses in front of it, and finally lies on its inner side. Instead c crossing in front of the vessel it may pass behind it. The median nerv gives off no branches in the arm, but sometimes receives a branch c communication from the musculo-cutaneous. The ulnar nerve lies o: the inner side of the artery as low as the insertion of the coraco-brachialk Parting company with the brachial artery, it descends with the ulna collateral artery, with which it passes through the medial intermuscula septum to the interval between the olecranon and medial epicondyle It has no branches in the arm. After the musculo-cutaneous nerv has traversed the coraco-brachialis, it passes obliquely downward and outwards between the biceps superficially and brachialis deeply In the region of the elbow it appears at the outer border of th biceps, and descends into the forearm as the lateral cutaneous nerv of forearm (p. 465). It supplies the coraco-brachialis (before reach ing it), and distributes branches to the biceps and brachialis as i lies between them. It sometimes communicates with the medial nerve.

The Cubital Fossa (Fig. 286).—This is the triangular hollow infron of the elbow. In the roof of the space are the skin, the median basili< and median cephalic veins, the medial cutaneous nerve of forearm, th< musculo-cutaneous nerve, deep fascia, and bicipital aponeurosis. Th< floor is formed by brachialis and a small part of supinator. The bas< is represented by an imaginary line connecting the epicondyles of th< humerus. The outer boundary is formed by the brachio-radialis, th( inner by the pronator teres; the two muscles converge as they extenc downwards, and the apex of the space is the point where their adjaceni margins meet, the pronator teres disappearing here under cover o: the brachio-radialis. The space contains the terminal part of the brachial, and the commencement of the radial and ulnar vessels. Or the outer side of the brachial artery is the tendon of the biceps, anc on its inner side is the median nerve. Under cover of the brachioradialis the radial nerve gives off its posterior interosseous branch.

Back of the Arm.

Triceps (Fig. 287)— Origin .—The long head arises by tendon frorr tne infraglenoid tubercle of the scapula. The lateral head arises frorr the outer part of the posterior surface of the humerus, extending a c high as the insertion of the teres minor, and as low as the spiral groove and slightly from the back of the lateral intermuscular septum abov( the level at which the radial nerve passes through it. The medial heat arises from the posterior surface of the humerus below the spiral groove reaching upwards on the inner side of the groove as high as the in sertion of the teres major, the whole extent of the back of the media intermuscular septum, and the back of the lateral intermuscular septun below the level at which the radial nerve passes through it.




THE UPPER LIMB


459


Insertion .—By a tendon attached to the back part of the upper surface of the olecranon process of the ulna, and slightly into the posterior ligament of the elbow-joint. An expansion from the outer side of the tendon sweeps downwards Dver the anconeous muscle, and blends with the deep fascia of the forearm.

The long and lateral heads end in a broad flat tendon occupying the lower part of the arm, the fibres of the long bead ending on its inner side, those of the lateral head on its upper and outer parts. Most of the fibres of the medial bead end on the deep surface of the tendon, but the lowest fibres are attached directly to the olecranon. The deepest md lowest fibres of the inner head are inserted into the posterior ligament of the elbow-joint, forming the so-called subanconeous. There is usually a bursa Dver the front part of the upper surface }f the olecranon, separating the tendon the muscle from the posterior ligament }f the elbow-joint.

The long head is related to the lower Dart of the capsular ligament of the

houlder-joint. Nerve-supply .—Branches of the radial

ontaining fibres from the sixth, seventh, md eighth cervical nerves.

Action. — Extends the elbow-joint, rhe long head also extends the shoulderoint.

The Radial (Musculo - spiral) Nerve

Fig. 288) lies at first behind the third )art of the axillary artery, between it md the subscapularis, and at a lower evel behind the upper part of the )rachial. Thence it passes downwards md backwards, with the profunda artery,

>etween the long and medial heads of he triceps, and winds round the back >f the humerus in the spiral groove, lying >etween the attachments of the lateral


Fig. 287. — Humerus, with Attachment of Triceps and Radial Nerve, seen from Behind.


md medial heads of the triceps. Passing through the upper part of he lateral intermuscular septum, it descends into the groove between he brachio-radialis and brachialis a little way above the lateral epiondyle, where it gives off the posterior interosseous nerve.

Branches —Medial Branches .—Arise on the inner side of the humerus.



460


A MANUAL OF ANATOMY


Muscular branches supply the long and medial heads of the tricep the branches to the long head are short and enter its upper part. T 1 branch to the medial head, or ulnar-collateral nerve, is a long, slend<


1 ig. 288. The Radial Nerve and the Profunda' Artery from

Behind.

lh ° arulmt?!! c°+L the , trice P s bee n partially removed to expose the arter

muscle ha? h e ^- ^ °? I 330 **- the humerus. The lower part of th

suDulies fhe 6611 mcisec ^ vertically to display the nerve which terminall

nerve at the bacTrf el ° ngated “^gement on th


ofthe ™ 1C * accompanies the ulnar nerve and enters the lower par

common ,, i f - 1, ' 16 posterior cutaneous nerve of arm often arises ii

common with one of the muscular branches; it is distributed to th








THE UPPER LIMB


461


skin on the back of the arm, and extends downwards nearly as low as the elbow.

Posterior Branches arise behind the humerus, and are distributed to the lateral and medial heads of the triceps and to the anconeus. The nerve to the anconeus is the terminal twig of one of the largest branches supplying the inner head. This branch passes downwards through and distributes branches to the muscle, finally escaping from its lower edge to end in the anconeus. As this nerve lies on the back of the elbow-joint it presents a small elongated swelling (pseudoganglion).

Lateral Branches appear on the outer side of the humerus, and are cutaneous, muscular, and articular. The lower lateral cutaneous nerve of arm and the posterior cutaneous nerve of forearm have been already described (p. 448). The muscular branches supply the brachioradialis, extensor carpi radialis longus, and brachialis, the last branch being inconstant. The articular branches are distributed to the elbow-joint.


The Shoulder-Joint.

The articular surfaces are the glenoid cavity of the scapula and the head of the humerus. The glenoid cavity is deepened by the labrum glenoidale, a circumferential rim of fibro-cartilage. The joint is surrounded by a capsular ligament with which certain accessory ligaments, the coraco-humeral and gleno-humeral, are associated.

The capsular ligament (Fig. 289) is attached to the margin of the glenoid cavity of the scapula, close to the labrum glenoidale, with which many of its fibres are connected. Above it extends to the root of the coracoid process, and below it is related to the long head 3f the triceps. At the humerus it is attached to the bone bordering the articular surface, and extends for some little distance on to the shaft, this being more particularly the case below. The ligament is so extensive and loose that when the surrounding muscles are divided the head of the humerus can be withdrawn from the glenoid cavity for 1 distance of an inch or more. The ligament presents two deficiencies, dne, the foramen ovale, is situated in front, behind the tendon of the mbscapuiaris. Through it the synovial membrane of the joint is con:inuous with a large bursa underlying the subscapularis, and intervening between it and the neck of the scapula. Opposite the upper md of the bicipital groove of the humerus the attachment of the 'apsular ligament to the bone is interrupted, and it blends there with be transverse ligament. This interruption gives passage to the tendon )f the long head of the biceps, which as it descends into the canal formed )y the bicipital groove bridged over by the transverse ligament is nvested by a synovial sheath continuous above with the synovial nembrane of the joint. A deficiency on the posterior aspect of the capsule, whereby 'the synovial membrane is continuous with a bursa mderlying the infraspinatus, is sometimes present.


462


A MANUAL OF ANATOMY


The coraco-humeral ligament is a strong band which extends fror the root and inferior aspects of the coracoid process to the greate tuberosity of the humerus. It strengthens the upper part of th capsule, with which it is closely blended.

The gleno-humeral ligaments (Fig. 291) are three thickenings c the capsular ligament projecting from its deep surface into the joinl They are best studied by opening the shoulder-joint from behinc and examining the deep surface of the anterior part of the capsula ligament from this point of view. The superior extends from th upper end of the anterior margin of the glenoid cavity to the lesse


coraco*acromial licj \


coraco


-hcti


svjnov. memk

jibres briolcjincj bicipital cjroove


icep;


tend


on


jularis


Fig. 289.—The Shoulder-Joint from in Front.

The subscapularis has been reflected to expose the bursa between it and the neck of the scapula, and the continuity of this bursa with the synoviai membrane of the joint.


tuberosity of the humerus. It is closely applied to the front edge of the tendon of the biceps, to the presence of which it is largely due. The middle (Flood s ligament) is inseparable from the superior at its glenoid attachment, but diverges from it as it extends downwards lower P ar t the lesser tuberosity. It has a well-defined upper edge, forming the lower boundary of the deficiency in the front of the capsular ligament, this deficiency being covered in front by the tendon of the subscapularis. The inferior (Schlemm’s ligament) extends from about the middle of the anterior margin of the glenoid cavity to the inferior aspect of the head of the humerus. With the








THE UPPER LIMB


463

xception of its upper edge, it is a somewhat ill-defined band diich below merges imperceptibly with the general capsular liganent.

The transverse ligament, with which the capsular ligament blends p. 461), consists of transverse fibres which extend between the two uberosities of the humerus, and bridge across the upper end of the •icipital groove.

The labrum glenoidale is a dense fibro-cartilaginous ring, triangular 1 section, the base being implanted on the edge of the glenoid cavity, t deepens the glenoid cavity for the reception of the head of the umerus. Peripherally it is connected with the capsular ligament, nd above is incorporated with the tendon of origin of the long head f the biceps.


Fig. 290.—The Right Glenoid Cavity and the Adjacent Ligaments.


The tendon of the long head of the biceps may be regarded as a rpplementary ligament, as it straps over the head of the humerus, nd is concerned in preventing its upward displacement.

The synovial membrane may be traced from the free margin of le labrum glenoidale on to its outer aspect, and thence on to the eep surface of the capsular ligament, for which it provides a compete lining. It is reflected from the humeral attachment of the ipsular ligament, and provides a slight investment for the bone grounding the articular head of the humerus, especially below, r here it is prolonged for some little distance downwards on the inner spect of the shaft. It ceases at the margin of the cartilage clothing le head of the humerus. Through the deficiencies on the front constant) and back (occasional) of the capsular ligament, it is connuous with the bursae underlying the subscapularis and infraspinatus "spectively. A fold of the synovial membrane is reflected from the







4 6 4


A MANUAL OF ANATOMY


upper part of the capsular ligament, and surrounds the tendon of t] long head of the biceps, which is thereby excluded from the synovi cavity. This fold is continuous with the synovial sheath investii the tendon of the biceps as it lies in the bicipital groove.

Muscular Relations.— Above, the supraspinatus; behind, from abo^ downwards, infraspinatus and teres minor; below, long head of tl triceps; and in front, subscapularis. The tendons of all these muscf are all more or less intimately blended with the capsular ligamen

Nerve-supply.—The suprascapular and circumflex nerves.

Movements. —As regards both range and variety of movement, the shoulde joint enjoys a greater mobility than any other joint in the body. Flexio


The posterior part of the capsular ligament has been removed, and the hea of the humerus withdrawn from the glenoid cavity to bring the three glenc humeral ligaments into view.


extension, abduction, adduction, a combination of these four movements takin

place in succession or circumduction, and rotation, all occur with considerab freedom.

Bursae.—1 he subscapular bursa lies between the tendon of th subscapularis muscle and the neck of the scapula, from which it extend outwards and overlaps the capsular ligament. It is continuous wit the synovial membrane of the joint through the foramen ovale.

The subacromial or subdeltoid bursa, one of the largest bursae i the body, is situated under cover of the acromion process of th scapula, the coraco-acromial ligament, and the acromial portion c the deltoid muscle. It intervenes between these structures and tt





THE UPPER LIMB


465


Dper part of the capsular ligament, together with the tendons inrted into the greater tuberosity of the humerus. It is usually multicular, and is independent of the synovial cavity of the joint.

The bursa of the infraspinatus muscle is not constant. When •esent, it is situated between the tendon of that muscle and the ick part of the capsule. It may communicate with the synovial embrane of the joint.

The bursa of the latissimus dorsi muscle is situated between the ndon of this muscle and that of the teres major close to their in;rtions.


Fig. 292. —Scheme to show Relations of Shoulder Capsule.

CR, acromion; SSP, supraspinatus; SS, subscapularis; CN, circumflex nerve; TM, teres major; T, long head of triceps; TMi, teres minor; ISP, infraspinatus; B, long tendon of biceps.

The bursa of the teres major muscle is situated behind the tendon f this muscle between it and the shaft of the humerus.

The bursa of the coraco-clavicular ligament is situated between te conoid and trapezoid ligaments.

The bicipital synovial sheath invests the long tendon of the biceps 1 the upper part of the bicipital groove of the humerus.

The Forearm and Hand.

Cutaneous Nerves (Figs. 280, 293).—On the outer side of the front f the forearm is the lateral cutaneous nerve of forearm, on its inner de the medial cutaneous nerve of forearm. A small cutaneous branch f the ulnar nerve occasionally supplies the skin about the middle

30










A MANUAL OF ANATOMY


466

of the front of the forearm; it is disposed on the inner side of the med cutaneous of forearm, with which it communicates.

On the outer side of the back of the forearm is the posterior bran of the lateral cutaneous of forearm; on its inner side the poster: branch of the medial cutaneous of forearm. Between the two is t posterior cutaneous of forearm.

The skin of the palm of the hand is supplied by the palmar cutaneo branches of the ulnar, median, and the terminal branches of the latei cutaneous of forearm. The palmar cutaneous branch of the ulr arises about the middle of the forearm, and descends for some distan


Iug. 293.—Plan of the Cutaneous Nerve-Supply of the Dorsum of tp

Hand and Fingers.

m and u are branches of the palmar digital nerves derived from the medic

nerve and ulnar respectively.

in front of the ulnar artery. As it approaches the wrist, it travers( the deep fascia and becomes cutaneous on the outer side of the tendo of the flexor carpi ulnaris. It passes in front of the flexor retinacului and is distributed to the skin of the inner part of the palm. Th palmar cutaneous branch of the median arises a little above the wris and traverses the deep fascia just above the flexor retinaculum, i the interval between the tendons of the flexor carpi radialis and th palmaris longus. It descends superficially to the flexor retinaculun a . ^ distributed to the skin of the central part of the palm, an

slightly to that of the thenar eminence. It communicates internall with the palmar cutaneous branch of the ulnar nerve, and lateral!







THE UPPER LIMB


467


ith that of the lateral cutaneous of forearm. The terminal branch

the lateral cutaneous of forearm is distributed to the skin of the lenar eminence. It communicates with a branch of the radial nerve, hich may take some small share in supplying the skin of the thenar ninence.

The skin on the dorsum of the hand and of the fingers is supplied by le radial nerve and the dorsal branch of the ulnar (Fig. 293). The idial nerve winds backwards deeply to the tendon of the brachioidialis about 3 inches above the wrist, and divides into two branches -lateral and medial. The lateral branch supplies the outer side of the ack of the thumb, and may supply some of the skin of the thenar ninence. The medial branch communicates with the terminal branch of le lateral cutaneous of forearm, sends a branch to the back of the rist, communicating with the dorsal branch of the ulnar, and divides ito four digital nerves. The first supplies the inner side of the thumb, le second the outer side of the index finger, the third divides into vo collateral branches supplying the adjacent sides of the index and liddle fingers, and the fourth passes to the cleft between the middle id ring fingers.

The dorsal branch of the ulnar nerve arises about 2J inches above le wrist, and winds backwards deeply to the tendon of the flexor irpi ulnaris. It sends a branch to the back of the wrist, which )mmunicates with a branch of the radial, and subdivides into digital ranches: one supplies the inner side of the little finger; a second ipplies the skin lining the cleft between the little and ring fingers, id gives a branch to the cleft between the ring and middle fingers, /erlapping the supply of the radial to these two fingers. It also ipplies the skin of the back of the hand.

The extent to which the skin on the dorsum of the hand and of the fingers supplied by the ulnar nerve and by the radial nerve respectively varies conderably, and the above description refers to the average arrangement only.

The dorsal digital nerves do not extend to the finger-tips, and are ipplemented by branches of the palmar digital branches of the median and ulnar nerves, passing backwards and supplying the skin ivering the more distal parts of the fingers. As a rule, the dorsal gital nerves extend farther on the marginal digits than they do 1 the central, reaching the base of the nail of the thumb and of the ttle finger, the distal interphalangeal joint of the index finger, and 1 the ulnar side of the ring finger, but only supply the skin on the ick of the proximal phalanx of the middle finger and of the radial de of the ring finger.

Veins. —On the back of the hand is a dorsal venous plexus, and smaller less important plexus occupies the front of the wrist. The )rsal venous plexus receives the superficial digital veins, which >mmence in plexuses in the region of the nails. Two in each finger, ie digital veins are placed one on either side towards the dorsal aspect, he two veins communicate with one another on the backs of the


A MANUAL OF ANATOMY


468

fingers above and below the interphalangeal joints. At the clef the two collateral veins, from the adjacent sides of two fingers, uni to form a single trunk, which ends in the dorsal venous plexus. T 1 superficial digital vein from the inner side of the little finger is co: tinuous with the posterior ulnar vein. The outer side of the dors venous plexus is drained by the radial and median veins, the inn side by the ulnar veins. The radial vein communicates with the de( veins at the proximal end of the first interosseous space; the poster! ulnar vein has also a deep communication in the region of the wris The venous plexus on the front of the wrist receives small veins from tl palm; it is drained by the median and anterior ulnar veins.

Deep Fascia of the Forearm. —The deep fascia is of considerab strength, its fibres being mainly transverse; some, however, are di posed longitudinally and obliquely. Above it blends with the t cipital aponeurosis, and behind receives an accession of fibres fro: the tendon of the triceps. In front of the elbow it presents an openir for the passage of the deep median vein. In the region of the ep condyles it serves as a common tendon of origin to the muscles arisir from these prominences, and is continuous with strong intermuscul; septa between them. These septa afford additional origin to tl muscles, and are easily recognized on the surface as white lines. It attached above to the epicondyles of the humerus, to the margins < the triangular surface on the back of the olecranon process, and on tl back of the forearm to the posterior subcutaneous border of the uln: The deep fascia is thicker and stronger on the back of the forearm tha it is on the front, and in the upper part of the forearm than it is in tl lower. On the front of the wrist it blends with the flexor retinaculun and at the back is thickened to form the extensor retinaculum.

Front of the Forearm.

Muscles. —The muscles of the front of the forearm are disposed i two layers—superficial and deep.

Superficial Layer (Fig. 294).—The muscles of this layer are fiv in number—pronator teres, flexor carpi radialis, palmaris longu flexor digitorum subJimis, and flexor carpi ulnaris.

Ihe five muscles have a common attachment to the medial ep condyle of the humerus, from which they diverge fanwise as the descend; the outermost, the pronator teres, crosses the upper part < the forearm obliquely; the innermost, the flexor carpi ulnaris, descent vertically and occupies the inner margin of the limb. The flext digitorum sublimis is only partially superficial, appearing betwee the flexor carpi ulnaris and the palmaris longus; the greater part < the muscle lies deeply to the palmaris longus, the flexor carpi ulnari and the pronator teres. The five muscles, in addition to their commc origin from the medial epicondyle, have extensive attachments t the deep fascia covering them, and to the intermuscular septa inte venmg between each muscle and the adjoining muscles. Three of the



THE UPPER LIMB


469

-the pronator teres, flexor digitorum sublimis, and flexor carpi ulnaris —have second or supplementary heads of origin from the bones of he forearm.

Pronator Teres arises by two heads. The superficial or humeral \ead is considerably the larger, and arises from the front and upper >art of the medial epicondyle and lower part of the medial supraconlylar ridge of the humerus; the deep fascia covering it; and the internuscular septa between t and the flexor carpi adialis medially, and lexor digitorum sublimis leeply. The deep or ulnar ead is small, and arises rom the inner margin of he rough triangular area >n the inferior aspect of he coronoid process of he ulna; it joins the deep urface of the superficial lead at an acute angle.

Insertion. — By means f a flat tendon into a ough impression about he middle of the outer urface of the radius, and t the summit of the onvexity of the outward urve involving the shaft f the bone.

Nerve-supply. —Branhes of the median, the bres of which are derived

om the sixth cervical erve. The branches to ie two heads are usually idependent, and arise '°m the median above the

vel of the elbow-joint. The muscle is directed awnwards and outwards.

Action. —Pronates the forearm, and assists in flexing the elbow)int.

The median nerve lies between the two heads of the muscle; the Lnar vessels are on its deep aspect, and the radial vessels and nerve oss it superficially close to its insertion.

The muscle may have a third head, arising from the medial intermuscular ptum of the arm, or from a supracondylar process, and, when present, bridges r er the brachial artery and median nerve.


i

1.


a


■ I ;



-Coraco-Brachialis


-Scapular Head of Triceps


Medial Head of Triceps


Brachio-Rad.


Rad. Extensors

l


w


...


Biceps

Brachialis

Pronator Teres Sup. Head . Bicipital Apon


F. Carpi Rad.

Palmaris Long. ,F. Dig. Sublimis

.F. Carpi Ulnaris


1


Abd. Poll. Long.. Pronator Quad._


Fig. 294. —Front View of Muscles of ‘ Free ' Upper Limb.




470


A MANUAL OF ANATOMY


The deep or ulnar head of pronator teres is relatively larger in the hum embryo than it is in the adult. It may be independent of the main part of 1 muscle, or may be associated with one of the adjoining muscles— e.g., the flei carpi radialis or palmaris longus. Possibly it represents the proximal end a deep pronating muscle, present in some animals, occupying the whole ext( of the radius and ulna, and of which the pronator quadratus is a distal surviv

Flexor Carpi Radialis (Fig. 294)— Origin .—The front of the med epicondyle; the deep fascia covering it, and the intermuscular sep separating it from pronator teres laterally, the palmaris longus medial] and the flexor digitorum sublimis deeply.

Insertion. —The front of the base of the second metacarpal bor and by a small slip into the front of the base of the third.

The muscle has a fusiform, fleshy belly in the upper half of t forearm, and a strong, flat tendon in the lower half.

Nerve-supply. —A branch of the median, containing fibres from t sixth cervical nerve.

The muscle extends from the inner side of the elbow towards t outer side of the wrist.

Action. —Flexes the wrist, and assists in flexing the elbow.

The tendon of the muscle passes through a special compai ment of the flexor retinaculum, where it occupies the groove on t] trapezium. The radial vessels lie to the outer side of the tendon the lower part of the forearm.

Palmaris Longus (Fig. 294)— Origin .—The front of the medi epicondyle; the deep fascia covering it; and the intermuscular sep separating it from the flexor carpi radialis laterally, flexor carpi ulnai medially, and flexor digitorum sublimis deeply.

Insertion .—The central division of the palmar aponeurosis, wi which it is continuous, and the front of the flexor retinaculum.

Nerve-supply .—A branch of the median, containing fibres of t] sixth cervical nerve.

Action. —Renders tense the central part of the palmar aponeuros: and assists in flexing the wrist and elbow-joints.

The palmaris longus is a very variable muscle, and is not infrequently absei It is the representative of a superficial flexor of the proximal phalanges, t distal part of which persists as the palmar fascia and its digital slips.

Flexor Digitorum Sublimis (Fig. 296)— Origin .—The upper < humero-ulnar head has an extensive and continuous attachment 1 the medial epicondyle above, the medial ligament of the elbow-joi] intermediately, and below to the tubercle marking the upper limit the ridge on the inner side of the rough triangular area on the inferi< aspect of the coronoid process of the ulna. The lower or radial hcc is broad and thin; it arises from the anterior oblique line of the radiu The fibres of both heads also arise from the deep aspect of an inte muscular septum between it and the overlying muscles.

ra( hal head are mainly associated with the tendon of b

middle finger.


THE UPPER LIMB


47 i


Insertion .—By four tendons attached to the four fingers. Each tendon ultimately subdivides into two slips, which are attached on either side of the shaft of the middle phalanx.

In the lower part of the forearm the muscle fibres are replaced by four tendons, which are disposed in pairs as they cross the front of the wrist deeply to the flexor retinaculum, the tendons destined for


Biceps


Brachialis —


Brachio-radialis

Flexor Digitorum Sublimis

Flexor Pollicis Longus

Pronator Quadratus Flexor Retinaculum


— — Pronator Teres


- - Flexor Carpi Radialis


- - Palmaris Longus


-Flexor Digitorum Sublimis


-Flexor Carpi Ulnaris


_Palmaris Brevis


Fig. 295. —The Superficial Muscles of the Front of the Forearm.


die middle and ring fingers lying in front of those for the index and little fingers. In this situation they are invested by the great palmar synovial sheath (p. 491). In the palm the four tendons diverge, ^ach tendon being accompanied by a tendon of the flexor digitorum profundus, which lies deeply to it. On the finger each pair of tendons is contained in the digital sheath, a fibrous arcade which, with the















472


A MANUAL OF ANATOMY


Brachial Artery Median Nerve


Biceps


Brachio-radialis

Radial Nerve, Radial Recurrent Artery Radial Artery


Superficial Head of Pronator Teres (cut)


Flexor Pollicis Longus

Radial Artery Brachio-radialis

Flexor Carpi Radialis Pronator Quadratus Abductor Pollicis Longus


Abductor Pollicis Brevis Flexor Pollicis Brevis


•Brachialis


-Superficial Head of Pronator

Teres (cut)

-Flexor Carpi Radialis

-- Ulnar Artery

■ “' Palmaris Longus


”**, Deep Head of Pronator Teres


-Flexor Carpi Ulnaris


-Flexor Digitorum Sublimis


Median Nerve Palmaris Longus Ulnar Artery Ulnar Nerve

-Flexor Carpi Ulnaris


,-Palmaris Brevis


-.Palmar Aponeurosis


Fig. 296.- I HE pRONT OF THE FOREARM, AND PALM OF THE HAND.






































THE UPPER LIMB


473


palmar aspects of the proximal and middle phalanges, completes a unnel in which the tendons are contained. Opposite the base of the )roximal phalanx the flexor sublimis tendon splits into two parts to dlow the tendon of the flexor profundus to pass through it. The two )arts of the superficial tendon are folded round the deep tendon, and mite on its deep aspect towards the distal end of the proximal phalanx, finally, the superficial tendon splits for a second time into its two ilips of insertion.

Nerve-supply .—Branches from the median containing fibres from he sixth cervical nerve.

Action .—Flexes the middle phalanges of the four fingers; further contraction of the muscle flexes the metacarpo-phalangeal joints and he wrist; it also assists in flexion of the elbow-joint.

The Flexor Carpi Ulnaris arises by two heads. The humeral head irises from the front of the medial epicondyle; from the deep fascia covering it, more particularly from the bicipital aponeurosis, as it fiends with the deep fascia; and the intermuscular septa between it ind the palmaris longus and the flexor digitorum sublimis. The ulnar lead arises from the inner aspect of the olecranon process, and indirectly rom the upper two-thirds of the posterior border of the ulna, by means )f the deep fascia which is attached to this border, and from which he fibres of the muscle arise.

Insertion .—The pisiform bone. Fibres of the tendon of insertion ire also prolonged into the piso-hamate and piso-metacarpal ligaments, he former being attached to the hook of the hamate bone, the latter o the base of the fifth metacarpal. An expansion from the outer ide of the tendon blends with the flexor retinaculum.

Nerve-supply .—Branches of the ulnar containing fibres from the Ighth cervical and first thoracic nerves.

The fibres of the muscle are directed downwards and forwards, md are implanted on the posterior and inner aspects of the tendon, vhich commences about the middle of the forearm.

Action .—Flexes and adducts the wrist-joint, and is a feeble flexor )f the elbow-joint.

The ulnar nerve and posterior ulnar recurrent artery lie between he two heads of the muscle.

The Radial Artery is one of the two terminal branches of the brachial vhich, in the cubital fossa and opposite the upper part of the neck >f the radius, subdivides into the radial and ulnar arteries. It is mailer than the ulnar, and its direction is at first continuous with hat of the parent trunk. The upper part of the vessel curves downwards and outwards, but for the greater part of its extent it descends r ertically downwards in the forearm. At the lower end of the forearm ts direction suddenly changes, and it winds round the outer side of the wrist, below the styloid process of the radius, and lying on the lateral igament of the wrist-joint. Gaining the back of the wrist, it descends or a short distance to the proximal end of the interspace between the Lst and second metacarpal bones, where it passes forwards between


474


A MANUAL OF ANATOMY


the two heads of the first dorsal interosseous muscle (abductor indici into the palm, and there joins the deep branch of the ulnar artery complete the deep palmar arch. The vessel may consequently be su

divided into three parts, occupying tl forearm, the back of the wrist, and tl palm respectively.

The First Part extends from the orig: to the styloid process of the radius. I direction as a whole is downwards ar slightly outwards. Its course may be ii dicated by a line drawn from a point ju: below the bend of the elbow, midway b tween the epicondyles of the humerus, to point about \ inch medial to the styloi process of the radius. The upper part < the vessel lies between the brachio-radial laterally and pronator teres medially, an is overlapped by the fleshy belly of tl former muscle. For the rest of its exter it is placed between the brachio-radial laterally and the flexor carpi radialis med ally. In the lower part of the foream where these muscles are replaced by tendon; the vessel is quite superficial.

Relations — Superficial .—The inner mai gin of the brachio-radialis in the uppe third, or more. Deep .—From above dowr wards it lies upon the tendon of insertio of the biceps; supinator; the pronator terc close to its insertion; the radial head of th flexor digitorum sublimis; the flexor pollici longus; the pronator quadratus; and th lower end of the radius. Lateral .—Th brachio-radialis for the whole extent of th forearm. In the upper part of the foreari the radial nerve is at some distance from : and to its outer side, but is a close latera relation for about the middle third of th forearm. Some distance above the wrh the nerve leaves the artery, and winds t the back of the limb under cover of th tendon of the brachio-radialis. MedialThe pronator teres in the upper third of th forearm, and for the rest of its extent tl' . flexor carpi radialis. The radial artery

accompanied by two venae comites, placed one on either side of ii and connected together by numerous transverse communications. * ranches of the First Part. —Numerous small, irregularly dispose


ITg. 297.-To SHOW THE

Course and Deep Relations of the Radial Artery.







THE UPPER LIMB


475

branches are distributed to the muscles and skin. In addition it has three more constant branches.

The radial recurrent artery arises from the outer side of the radial close to its commencement. It passes upwards deeply to the brachioradialis, and lies in front of supinator. Some of its branches are distributed to the muscles arising from the lateral epicondyle, others to the elbow-joint. One branch ascends with the radial nerve between the brachio-radialis and brachialis, and anastomoses in front of the lateral epicondyle with the anterior terminal branch of the profunda artery.

The anterior carpal branch is a small artery which arises from the inner side of the radial at the level of the lower border of the pronator quadratus, and passes inwards, lying deeply to the flexor tendons. It breaks up into small branches which anastomose with the anterior ulnar carpal artery to form the anterior carpal network or rete. This rete is joined from above by the anterior terminal branch of the anterior interosseous artery, and from below by recurrent branches of the deep palmar arch. Branches of the rete are distributed to the wrist-joint and the carpal articulations.

The superficial palmar branch arises below the preceding branch, and passes downwards superficial to, or through, the muscles of the thenar eminence, in which it may end. It usually reaches the palm, and ends by anastomosing with the ulnar artery to complete the superficial palmar arch.

Varieties of the First Part. —(i) The artery may arise from the upper part of the brachial, or from the axillary. (2) When of high origin, it may descend superficially to the bicipital aponeurosis of the biceps and deep fascia of the forearm. ( 3 ) The artery may wind backwards superficially to the brachio-radialis just below the middle of the forearm. (4) It may be joined by a vas aberrans from the brachial, or from the axillary. (5) It may end at the lower part of the forearm, its distribution being replaced by branches of the ulnar, median, or anterior interosseous.

The second and third parts of the radial artery are described on pp. 509 and 497.

Radial Nerve. —Having given off its posterior interosseous branch, the radial nerve descends deeply to the brachio-radialis, lying at first at some distance to the outer side of the radial artery, and accompanies it for about the middle third of the forearm. It finally winds round the lower end of the radius, under cover of the brachioradialis, to the back of the limb, where it becomes superficial (p. 467). It has no branches in the forearm.

The Posterior Interosseous Nerve is described on p. 506.

The Ulnar Artery (Fig. 298) is the larger of the two terminal branches of the brachial, and arises in the cubital fossa opposite the upper part of the neck of the radius. Descending in the forearm, it reaches the palm by passing in front of the flexor retinaculum, and is thence prolonged into the hand as the superficial palmar arch. At first it curves downwards and inwards deeply to pronator teres, flexor carpi radialis,


A MANUAL OF ANATOMY


476


palmaris longus, and flexor digitorum sublimis. Having gained th< front of the ulna, it meets the ulnar nerve and descends on the oute] side of the nerve, both structures lying on the flexor digitorum pro fundus, and being overlapped superficially by the flexor carpi ulnaris A little above the wrist the artery may lie superficially on the outer side

of the tendon of the flexor carp


Radial Nv.’*

Post. Inteross. Nv. Biceps Tendon' Radial Rec. A.


Ant. Uln. Rec. A.

Post. Uln. Rec A.


Supin.-- ■


Inteross. A.


Pron. Teres >


Flex. Dig. Sub. Rad. Hd.


Radial Nv.—


Flex. Poll. Long.,

\a


Flex. Dig. Prof.


- , Ulnar Nv.


I


Pron. Quad. Superfic. Palmar Branch of Rad. A



Post. Carp. Branch of Ulnar A.


Ant. Carp. Branch of Rad. A.


Ant. Carp. Branch of Ulnar A.


ulnaris. It crosses in front of the flexor retinaculum, lying to the outer side of the pisiform bone, the ulnar nerve intervening betweer the two. On reaching the hand, it curves outwards in the palm towards the thenar eminence. The vessel may be divided intc three parts.

The First Part extends from the origin to the upper border of the flexor retinaculum. On account of the curve involving the upper part of the vessel, no definite line can be given to indicate its entire course. In the lower half of the forearm the edge of the flexor carpi ulnaris is a useful guide to its position.

Relations — Superficial. —In the upper half of the forearm the artery is deeply placed, being covered by pronator teres, flexor carpi radialis, palmaris longus, and flexor digitorum sublimis. In the lower half it is overlapped by the tendon of the flexor carpi ulnaris, except for a short distance above the wrist, where it may lie superficially on the outer side of the tendon. The palmar cutaneous branch of the ulnar


Fig. 298.—To illustrate the Deep nerve descends in front of the and Nerve Relations of the Radial artery in its lower half. Deep — and Ulnar Arteries. Brachialis for about I inch, and

. . for the rest of its extent the flexor

digitorum profundus. Lateral .—In its distal two-thirds the flexor digitorum sublimis. Medial .—The ulnar nerve for about its distal two-thirds, and possibly the tendon of the flexor carpi ulnaris for a short distance above the wrist. The nerves related to the first part of the arteiy are the median, ulnar, and palmar cutaneous branch of the) ulnar. At its commencement the median nerve lies to its inner side,










THE UPPER LIMB


477


but deeply to pronator teres the nerve crosses in front of it, the deep head of pronator teres intervening between them, and gains its outer side. The ulnar nerve, descending from behind the medial epicondyle, is at first separated from the artery by a considerable interval.

As the nerve and artery descend, they converge and pass downwards to the wrist, lying side by side. The palmar cutaneous branch of the ulnar nerve descends in front of the lower part of the vessel. The ulnar artery is accompanied by two venae comites, which are connected together by numerous transverse communications.

Branches of the First Part. —In

addition to numerous small muscular and cutaneous twigs, the ulnar artery gives off the following branches:

The anterior ulnar recurrent artery is a small vessel which passes upwards and inwards on brachialis and under cover of the superficial head of the pronator teres. It supplies these muscles and anastomoses with the anterior branch of the supratrochlear of the brachial.

The posterior ulnar recurrent artery, a larger vessel, arises immediately below the preceding, or sometimes in common with it. It passes inwards under cover of the flexor digitorum sublimis, and then ascends with the ulnar nerve between the two heads of the flexor carpi ulnaris to the interval between the medial epicondyle and olecranon process. It supplies the adjacent muscles, ulnar nerve, and elbow-joint, and anastomoses with the ulnar collateral and posterior branch of the supratrochlear. It also gives twigs which ramify on the back of the olecranon, anastomose with the posterior interosseous recurrent, and takes part in forming the olecranon rete.


Fig. 299. —The Anterior Interosseous Artery and Nerve.

The two deep flexor muscles have been pulled aside, and the pronator quadratus incised vertically.



















478


A MANUAL OF ANATOMY


The common interosseous artery (Figs. 299 and 300) is a short thick trunk, which arises below the preceding, and about 1 inch fron the commencement of the ulnar artery. It passes backwards to th< upper border of the interosseous membrane, where it divides into th< anterior and posterior interosseous arteries.

The anterior interosseous artery descends in front Of the interosseou: membrane with the anterior interosseous nerve on its outer side. I lies between the flexor pollicis longus laterally and the flexor digitorun profundus internally, being overlapped by the adjoining edges of th<

two muscles. At the upper borde: of the pronator quadratus it divide: into two terminal branches, anterioi and posterior.

Branches. — The median artery (comes nervi mediani) is a long slender branch which arises fron the commencement of the vessel and is frequently a direct brand of the ulnar artery. It is a close companion of the median nerve which it accompanies.

It may be a large vessel, and pas: deeply to, or in front of, the flexor reti; naculum into the palm, where it maj join the superficial palmar arch, or ma] terminate by furnishing digital arteries. ,

Muscular branches are given of to the deep layer of muscles, anc to the extensor muscles on the bad of the interosseous membrane. The branches to the latter muscles pas.* through the membrane. Nutrienl branches enter the radius and ulnti respectively. The anterior termina branch descends deeply to the pro nator quadratus, and joins the anterior carpal rete. The posterioi , terminal branch passes backwards

rough the interosseous membrane, and anastomoses with the posterior interosseous. It descends deeply to the extensor tendon* ancl the extensor retinaculum to the back of the wrist, where it end*

m the posterior carpal arch. The posterior interosseous artery L* described on p. 507. J

The posterior carpal branch arises a little way above the pisiforrr j one, and passes backwards under cover of the tendon of the flexoi carpi u nans to the back of the wrist, where it anastomoses with the) pos enor carpal branch of the radial artery to complete the posterioi


Fig. 300.—Deep Dissection of the Front of the Right Elbow.















THE UPPER LIMB


479


Radial Rec


Post-Interos

Rec.

Ant. Interos. A. Nut. to Radius


Ant. Uln.

' Rec. A.

Post. Uln.

Rec. A.

Com. Interos. Post. Interos. A Med. A.


Nut. to Ulna


carpal arch. It may give off a dorsal digital artery to the inner side )f the little finger.

The anterior carpal branch arises opposite the lower border of the pronator quadratus. It passes outwards along the lower border of hat muscle deeply to the flexor ligitorum profundus, and anastonoses with the anterior carpal iranch of the radial artery, the interior branch of the anterior nterosseous, and the recurrent ranches of the deep palmar arch, o form the anterior carpal rete.

Anastomoses about the Elbow roint. —The anastomoses of arteries

ibout the elbow-joint are very

mmerous. In front of the medial

picondyle of the humerus the an erior branch of the supratrochlear

>f the brachial anastomoses with

he anterior ulnar recurrent. Behind

he medial epicondyle the ulnar

ollateral and the posterior branch )f the supratrochlear anastomose

vith the posterior ulnar recurrent.

n front of the lateral epicondyle

he anterior terminal branch of the

>rofunda anastomoses with the

adial recurrent. Behind the lateral

picondyle the posterior terminal

iranch of the profunda anastomoses

dth the posterior interosseous re urrent. Upon the back of the shaft

•f the humerus, immediately above

he olecranon fossa, a transverse

nastomosis takes place between the

>osterior branches of the profunda

nd supratrochlear. Upon the back

f the olecranon process is the olec- Fig. 301.—To illustrate the Re anon arterial rete, supplied by lations of the Radial and Ulnar

•ranches of the nosterior interns- Arteries and their Branches to

eous recurrent and of the posterior THE Skeleton ' ™ Arteries i__ a m ui Liic pusiciiui taking part in the Formation of

r recurrent arteries. the Anterior Carpal Rete.


Ant Carp Br. of Rad.i


Post. Carp, r. of Uln. A.


Ant. Carp.

Br. of Uln. A.

Ant. Carp. Rete


Dp. Palm. Arch.


ulnar artery may have a high origin from the brachial, or rom the axillary. In cases of high origin the vessel usually lies superficially 3 he muscle s arising from the medial epicondyle of the humerus. In such ses the common interosseous is a branch of the main trunk, and furnishes the • ^ nor and posterior ulnar recurrent arteries. An ulnar artery, normal in ri gm, may lie superficially to the muscles arising from the medial epicondyle.









480


A MANUAL OF ANATOMY


The Second Part of the Ulnar Artery lies upon the flexor retinaculu

and extends from its-upper to its lower border. The ulnar nerve is ( its inner side. It lies on the outer side of the pisiform bone, but c the inner side of the hook of the hamate bone, where it is under cov of the piso-hamate ligament.

Relations — Superficial .—The expansion from the flexor car ulnaris tendon to the front of the flexor retinaculum, and the pis< hamate ligament. Deep. —The flexor retinaculum. Laterally. —T 1 hook of the hamate bone. Medially— The ulnar nerve and the pis form bone.

The third part of the ulnar artery is described on p. 487.

The Ulnar Nerve (Fig. 298).—The ulnar nerve gains the forean by passing downwards in the interval between the medial epicondy and olecranon process, and between the two heads of the flexor car] ulnaris. Descending under cover of that muscle, it lies upon tl flexor digitorum profundus. At about the junction of the upper thii with the lower two-thirds of the forearm it comes into relation with tl ulnar artery, and lies upon the inner side of that vessel for the rest < its extent in the forearm. It reaches the hand by passing in front < the flexor retinaculum close to the outer side of the pisiform bon At a lower level it lies to the inner side of the hook of the hamate bon

Branches.—Articular branches, two or three in number, suppl the elbow-joint and are given off from the nerve as it lies behind th medial epicondyle.

Muscular branches arise in the upper part of the forearm, an supply the flexor carpi ulnaris and the inner part of the flexor digitorui profundus.

The cutaneous branches are described on pp. 448 and 467.

The Median Nerve (Fig. 298).—In the cubital fossa the media nerve lies on the inner side of the brachial and ulnar arteries. 0 leaving the space it passes between the two heads of pronator tere; and here crosses in front of the ulnar artery, the deep head of the musci intervening between the two. Descending between the two heads c the flexor digitorum sublimis, it gains its deep aspect, and lies deepl to it until it approaches the wrist. Here it escapes from under cove of the muscle, and lies between it and the flexor carpi radialis. Cross ing the wrist on the deep aspect of the flexor retinaculum, it passe into the palm. It is accompanied by the median artery, a branch c the anterior interosseous. As the median nerve descends in the fore arm, it lies midway between the radial and ulnar arteries.

Branches.—Articular branches, one or two in number, enter th elbow-joint from in front.

Muscular branches supply all the muscles on the front of the fore arm, with the exception of the flexor carpi ulnaris and the inner par of the flexor digitorum profundus. The branches to pronator tere arise from the nerve above the level of the elbow-joint. The branche for the flexor carpi radialis, palmaris longus, and flexor digitorur sublimis arise from the nerve as it passes into the forearm. The flexc



THE UPPER LIMB


481


ollicis longus, outer portion of the flexor digitorum profundus, and proator quadratus are supplied by the anterior interosseous branch. This )ng branch arises from the median just below the neck of the radius, nd descends on the front of the interosseous membrane. It lies n the outer side of the anterior interosseous artery, the two being verlapped by the adjacent edges of the flexor digitorum profundus nd of the flexor pollicis longus. In the lower part of the forearm re nerve lies deeply to the pronator quadratus, and ends in two ranches; one enters the deep surface of the muscle, the other supplies re wrist-joint. The branch to the outer part of the flexor digitorum rofundus arises high up, and communicates in the substance of the mscle with the branch of the ulnar nerve supplying its inner part, he anterior interosseous nerve furnishes an interosseous branch istributed to the interosseous membrane. It gives off nutrient filalents which accompany the nutrient arteries to the radius and ulna.

Cutaneous Branch. —A short distance above the wrist a palmar daneous branch arises from the median nerve as it lies between the mdons of the flexor carpi radialis and the flexor digitorum sublimis.

I passes downwards in front of the flexor retinaculum, and is disputed to the skin covering the central part of the palm.

Deep Layer of Muscles (Fig. 298).—Consists of three muscles.

Flexor Digitorum Profundus — Origin. —The anterior and inner irfaces of the shaft of the ulna for about the upper three-fourths f their extent. The area of attachment extends from the posterior ibcutaneous border, to which the muscle is attached by means of fascial layer from which its fibres arise, to the interosseous or outer order. The area of attachment on the inner surface of the bone xtends upwards to the inner side of the olecranon process. From tie anterior surface of the ulna the attachment extends outwards on ' 3 the interosseous membrane, from the inner part of which it arises.

Insertion. —Towards the lower part of the forearm the muscle bres are replaced by tendon. The common tendon subsequently ivides into four tendons, which are inserted into the bases of the istal phalanges of the four fingers. The tendon of the index finger ecomes distinct from the main tendon some little way above the Tist; the other three on the front of the wrist under cover of the exor retinaculum. In the palm the four tendons diverge, and are ere associated with the four lumbrical muscles. Each tendon passes ito a fibrous flexor sheath of a finger accompanied by a tendon of tie flexor sublimis, deeply to which it lies, but opposite the shaft of tie proximal phalanx it passes through the tendon of the flexor submis in order to reach its more distal destination, the base of the distal halanx.

Nerve-supply. —A branch of the anterior interosseous nerve detved from the median, and containing fibres from the seventh and ighth cervical and the first thoracic nerves, supplies the outer part of P muscle; a branch of the ulnar nerve, containing fibres from the ighth cervical and first thoracic nerves, supplies the inner part.

31


482


A MANUAL OF ANATOMY


F. C. Uln- -F. D. Subl. Palm. L.


F. C. Rad.

Abd. Poll. Long


Action .—Flexes the distal phalanges of the four inner fingers; assis in flexing the middle phalanges and metacarpo-phalangeal joint and also assists in flexing the wrist-joint.

Flexor Pollicis Longus (Fig. 298)— Origin .—The anterior surfa of the radius, from the anterior oblique line above to the upper bord of the pronator quadratus below; the outer half of the front of t. interosseous membrane; and as a rule by a tendinous slip from t. inner margin of the coronoid process of the ulna, or more occasional from the medial epicondyle of the humerus.

Insertion .—The base the distal phalanx of t] thumb.

The tendon appears < the front of the muse about the middle of tJ forearm. The muscle fibr are attached obliquely ( either side of it, and e tend downwards to ne the wrist,

Nerve-supply .— branch of the anteri interosseous nerve, co taining fibres from t] seventh and eighth cervic and first thoracic nerves Action. — Flexes ti distal phalanx of ti thumb; assists in flexii its metacarpo-phalange joint; and is an auxilia flexor of the wrist-joint.

Pronator Quadratus (Fig. 298)— Origin .—The anterior surface the lower end of the ulna.

Insertion .—The anterior surface, and to a slight extent the inn aspect of the lower end of the radius.

Nerve-supply .—A branch of the anterior interosseous nerve, co

taining fibres from the seventh and eighth cervical and first thorac

nerves.


Fig. 302.—Front of Right Wrist, to show Relative Positions of Structures.


The fibres are disposed, for the most part, transversely, and t] muscle is covered by a dense fascial layer.

Action. Pronates the radius upon the ulna.


Front of the Wrist and Palm.

Landmarks. Below the styloid process of the radius the tuberc 01 the scaphoid can be felt, and below this the crest on the trapeziur n the inner aspect of the front of the wrist the pisiform bone ci




THE UPPER LIMB


483

asily be felt, and below and lateral to it (i.e., nearer the middle line f the wrist) is the hook of the hamate bone. The interval between tiese two projections indicates the position of the ulnar vessels and erve. The centre of the palm presents a triangular depression, the pex of which is directed upwards and inwards towards the wrist, nd the base downwards towards the roots of the fingers. In the latter tuation there is a transverse prominence, broken up by grooves iading to the three inner digits. The palmar depression is bounded iterally by the thenar eminence, and medially by the hypothenar minence.

The skin of the palm presents four furrows, two being disposed -ansversely, and two more or less longitudinally. The lower transerse furrow is about 1 inch above the roots of the inner three digits, nd is most conspicuous when the fingers are flexed. It commences t the inner border of the palm, and, passing outwards in a slightly rched manner, it terminates at the cleft between the index and addle fingers. It is produced by the flexion of the metacarpohalangeal joints of the inner three fingers. These joints are situated bout midway between this line and the roots of the fingers when these re extended. The upper transverse furrow commences at the outer Drder of the palm about f inch above the root of the index finger, id it passes inwards and slightly upwards to the inner border of le palm, lying about \ inch above the lower furrow. The outer irt of this furrow is due to flexion of the metacarpo-phalangeal joint

thg index finger, and the remainder to complete flexion of the metacarpo-phalangeal joints of the inner three fingers. One of the ngitudinal furrows commences about the centre of the wrist, and irves downwards and outwards to meet the upper transverse furrow, is produced by the movement occurring in the joint between the apezium and the first metacarpal bone when the thumb is opposed > the fingers. The second longitudinal furrow runs downwards om the wrist medial to the preceding, and meets the lower transverse arow. It is due to the movement of opposition of the little finger, he palmar aspect of each of the four fingers presents three transverse Trows. The distal pair correspond with the interphalangeal joints, it the proximal furrow is about \ inch below the metacarpo-phalangeal int. The thumb presents only two such transverse furrows. The vel of the free edge of the skin fold between any two fingers corresponds ' the middle of the proximal phalanx; the metacarpo-phalangeal int is at least f inch proximal to it.

The position of the superficial palmar arch corresponds to a curved ie drawn from the outer side of the pisiform bone parallel to the irved edge of the thenar eminence, and not extending into the palm iyond the level of the extended and abducted thumb. From the •nvexity of the arch three palmar digital arteries pass downwards line with the webs of the fingers, and occupy the intermetacarpal nces. An incision, therefore, may be made with safety in the palm the direction of the middle line of a finger, but it should not be


A MANUAL OF ANATOMY


484

carried nearer the wrist than the line indicating the position of t superficial palmar arch. The deep palmar arch lies about 1 in nearer the wrist than the superficial. The digital arteries are plac on the lateral aspects of the fingers.

On the back of the hand the dorsal radial tubercle may be f< about the middle of the lower end of the bone, and the heads of t metacarpal bones, which form the knuckles, are conspicuous wh the fingers are flexed. Towards the outer side of the wrist, when t thumb is abducted, is a well-marked triangular depression, the be of which is directed upwards. In this depression the pulsation the radial artery may be felt in the living subject. The depressi is bounded medially by the tendon of the extensor pollicis longi laterally by the tendons of the abductor pollicis longus and extern pollicis brevis, and above by the lower end of the radius. Lying deep in it are the tendons of the two radial extensors of the wrist. T scaphoid and trapezium form its floor, the commencement of the rad vein and branches of the radial nerve occupy the subcutaneo tissue superficial to it. This depression is known as the anatomu snuff-box.

The middle line of the hand, away from which and towards whi abduction and adduction of the digits naturally take place, is : presented by the axial line of the middle finger.

The Superficial Fascia covering the hollow of the palm is fim lobulated, the fatty lobules being separated by fibrous processes whi extend from the skin to the central part of the palmar aponeurosis.

The Palmaris Brevis (Fig. 303) is a thin, flat, subcutaneous muse quadrilateral in outline, and usually consisting of two or three bundl

Origin .—The front of the flexor retinaculum, and the inner map; of the central part of the palmar aponeurosis.

Insertion .—The skin covering the inner aspect of the hypother eminence.

Nerve-supply .—A branch from the superficial division of the ulr nerve.

Action .—Wrinkles the skin on the inner side of the palm, and drawing it towards the middle line of the hand probably renders f palm a more efficient grasping organ.

The muscle lies in the superficial fascia covering the proxin part of the hypothenar eminence, and in front of the ulnar vess and nerve.

The Superficial Transverse Ligament of Palm is composed of bundle of transverse fibres contained within the folds of skin whi limit the clefts between the four fingers.

The Palmar Aponeurosis (Fig. 303) consists of three parts—a cent

and two lateral.

the central part is triangular, the apex being towards the wri where it is mainly continuous with the tendon of the palmaris long its deeper fibres being continuous with the flexor retinaculum. T superficial fibres are longitudinal and the deep fibres transverse, 1



THE UPPER LIMB


485

itter being most conspicuous towards the fingers. The base is directed Dwards the four fingers, on approaching which it divides into four igital processes. These diverge and join the sheaths of the flexor


he pads of fat between the digital processes of the central part of the palmar aponeurosis have been removed in order to expose the digital arteries and nerves.

indons on the palmar aspects of the fingers. From each process bres pass to the superficial transverse ligament, and to the skin folds tmting the clefts between the fingers. Two deep prolongations are ven off, one from either side of a digital process, and join the trans












486


A MANUAL OF ANATOMY


verse metacarpal ligament on either side of the head of a metacar bone (p. 526). A digital process and its two deep prolongations fc the roof and the side walls respectively of a short canal in which two flexor tendons of a finger are contained. Between the f<


Fig. 304.— Dissection of Palm.


iy. e ^ ln fl digital processes are three intervals occupied by fat, k arteries and nerves and lumbrical muscles are er

v l ck 6 cen ^ ra ^ P ar t the palmar aponeurosis is bound to t.j s m y hbi 011s processes which enclose spaces containing very fine









THE UPPER LIMB


487

obulated fat. Its deep surface is related to the superficial palmar irch, the digital nerves, and the palmar synovial sheath investing the lexor tendons. From either margin a deep septum projects into the land and joins the interosseous fascia investing the flexor of the palm, rhe outer septum marks the inner limit of the thenar muscles, while he inner septum marks the outer limit of the hypothenar muscles, rhe central portion of the palmar aponeurosis forms the roof, the

wo septa the side walls, and the interosseous fascia the floor of a large central palmar compartment containing the flexor tendons, lumbrical nuscles, and the palmar bloodvessels and nerves. On either side of his central compartment are two marginal compartments, containing

he short muscles of the thumb and of the little finger respectively, rhe central part of the palmar aponeurosis affords protection to the superficial palmar arch and the digital arteries and nerves.

The central part of the palmar aponeurosis, together with the palmaris ongus, represent a superficial flexor of the proximal phalanges, a muscle present n some animals. The four digital slips and the two deep lateral prolongations vith which each slip is provided represent the four tendons of this muscle, each >f which subdivides before reaching its insertion, the base of the proximal )halanx, and thereby gives passage to the flexor tendons attached to the internediate and distal phalanges.

The lateral or thenar division is thin, and covers the thenar muscles. \bove it is connected with the tendon of the palmaris longus and lexor retinaculum; it also receives fibres from the tendon of the ibductor pollicis longus.

The medial or hypothenar division is also thin. It is connected ibove with the flexor retinaculum, and ends below by blending with he tendons of the muscles inserted into the inner side of the base of

he proximal phalanx of the little finger. The Third Part of the Ulnar Artery (Fig. 305) is the superficial )almar arch. It descends for a short distance deeply to the palmaris )revis and arches outwards across the palm. The arch is completed >y °ne of the branches of the radial artery—either the superficial >almar, the radialis indicis, or the princeps pollicis. The convexity of he arch is towards the fingers.

Relations — Superficial. —The skin and subcutaneous tissue, the >almaris brevis for a short distance, and the central division of the >almar aponeurosis. Deep .—From within outwards it rests upon the iexor digiti minimi, the digital branches of the ulnar nerve, the flexor endons, and the digital branches of the median nerve.

Branches. —Cutaneous to the skin of the palm, muscular to the djacent superficial muscles, the deep branch, and the digital branches.

The deep branch of the ulnar artery arises at the level of the lower ►order of the flexor retinaculum. It passes deeply into the palm, in ompany with the deep division of the ulnar nerve, between the abLuctor and flexor digiti minimi, and deeply to, or through, the opponens digiti minimi. It ends by joining the terminal part of the radial artery, nd with it completes the deep palmar arch.


4 88


A MANUAL OF ANATOMY


The palmar digital arteries arise from the convexity of the supc ficial palmar arch, and are four in number. They are destined for t


The superficial palmar arch is represented as completed on the outer side o

e and by communications with the superficial palmar and radiali mdicis arteries.


^ U PP y ° * e mner three and a half fingers, and are called first, second;

nra and fourth, from within outwards. The first digital artery i sma , an passes downwards and inwards over the hypothenar muscles












THE UPPER LIMB 489

0 which it gives twigs. It is distributed to the inner side of the little nger.

The second, third, and fourth digital arteries pass downwards owards the clefts between the fingers. Each one divides into two ollateral digital arteries which supply the adjacent sides of two ngers. The second digital artery supplies the adjacent sides of the ttle and ring fingers, the third those of the ring and middle fingers, nd the fourth those of the middle and index fingers. The outer side { the index finger and the two sides of the thumb are supplied respecively by the radialis indicis and princeps pollicis, branches of the adial artery. As the digital arteries approach the fingers they lie ►etween the flexor tendons, and superficial to the digital nerves and umbrical muscles. On the sides of the fingers, however, the digital lerves are superficial to the arteries. Shortly before the outer three iivide into their collateral branches each artery is joined by a palmar netacarpal artery derived from the deep palmar arch. The two rteries, one on either side of a finger, supply the structures on the )almar aspect of the phalanges and are connected together by numerous ransverse communications most marked on the proximal side of the nterphalangeal joints. Dorsal branches from these arteries are disributed to the structures on the back of the intermediate and distal )halanges. One well-marked dorsal branch joins with its fellow on he opposite side at the root of the nail, forming an arterial arcade, ranches of which supply the nail-bed. The two arteries end by oining one another in an arterial arcade on the palmar aspect of the listal phalanx, from which numerous twigs are given off to supply the r ery vascular pulp on the tip of the finger.

The Veins accompanying the superficial palmar arch and the digial arteries are very small, as the blood from the fingers is largely irained by vessels joining the plexus of veins on the dorsum of the land (p. 467).

The Median Nerve reaches the palm by passing deeply to the flexor etinaculum. In this situation it presents a distinct enlargement or iseudo-ganglion, and gives off articular twigs to the wrist-joint. At he lower border of the ligament it gives off a short muscular branch, vhich subdivides into three, and supplies the three superficial short nuscles of the thumb, the abductor pollicis brevis, opponens pollicis, aid flexor pollicis brevis. It finally subdivides into five digital ranches. The first and second supply the two sides of the thumb; he third gives a branch to the first or most lateral lumbrical muscle, aid supplies the outer or radial side of the index finger. The fourth aid fifth, as they approach the clefts between the fingers, both subdivide nto two collateral branches supplying the adjacent sides of two fingers, rhe fourth gives a branch to the second lumbrical muscle, and supplies he adjacent sides of the index and middle fingers; the fifth has a comnunicating branch with the adjoining digital branch of the ulnar nerve, aid supplies the adjacent sides of the middle and ring fingers. In the ialm the digital nerves lie deeply to the superficial palmar arch and


490


A MANUAL OF ANATOMY


its digital branches, but on the sides of the fingers the nerves are sup ficial to the arteries. Occasionally a digital artery may pass throu a digital nerve as the latter gains its superficial position. The digi nerves give branches to the skin on the palmar aspects of the finge and on these small swellings, called Pacinian bodies, are found. Th also supply the metacarpo-phalangeal and interphalangeal joints, the extremities of the fingers each nerve ends in branches for the pi of the tip of the finger. They also give dorsal branches which supj the skin on the back of the distal phalanges and the nail-beds (p. 461

Summary of the Median Nerve—Muscular. —It supplies all the muscles the front of the forearm, except the flexor carpi ulnaris and the inner porti


Ulnar

Median

Anteiior Branch Lateral Cutaneous of Forearm

Deep Branch of Ulnar Branches to Hypothenar Muscles

Branches to 3 Thenar Muscles


Branch to 1st Lumbrical

Branch to 2nd Lumbrical.^

Branch connecting Median and Ulnar


I ig* 3°6. Diagram of the Nerves of the Palm.


of the flexor profundus digitorum; the abductor, opponens, and flexor muscles. Cutaneous. —The palmar palm, and the digital branches the It supplies branches to the elbowof the hand.


three short muscles of the thumb—nam pollicis brevis; and the two outer lumbr cutaneous branch supplies the middle of outer three and a half digits. Articulai and wrist-joints, as well as to several joi


ynovial Sheaths (big. 3 ° 7 );—The flexor tendons occupying th cana > . e ro °f of which is the flexor retinaculum, are provide w } W fl s y novi al^ sheaths. The inner and larger invests the tendor ? f 5 xc J r syblimis and flexor profundus; the outer and smalki !T S I ] e Lt ll( ^ on of the flexor pollicis longus. The synovial sheatl r re ec e ^ i om the tendons, and line the wall of the canal in whic ey aie contained. The layer lining the roof of the canal covers th














THE UPPER LIMB


491


leep aspect of the median nerve. The two sheaths may be independent, >ut sometimes communicate with one another. Both sheaths are >rolonged for some distance upwards into the forearm, where they end it the level at which the tendons become continuous with the muscle >ellies. The outer sheath is prolonged downwards into the palm, and hence on to the thumb, following the tendon of the flexor pollicis ongus to its insertion at the base of the terminal phalanx. The inner heath is also prolonged into the palm, where it broadens as the tendons liverge. About the middle of the palm it ends in three small diverticula pposite the second, third, and fourth metacarpal bones. On the nner side, however, a prolongation follows the flexor tendons of the


'Sgs Flexor Retinaculum


__Synovial Sheath of Thumb


Common Synovial Sheath of Digital Flexor Tendons


_ _ Synovial Sheath 0 ? Little Finger


Fig. 307. —-The Synovial Sheaths of the Flexor Tendons.



ittle finger, and extends to the base of its terminal phalanx. The lexor tendons of the index, middle, and ring fingers are provided with independent sheaths, which, commencing at the distal ends of the espective metacarpal bones, are prolonged to the bases of the distal )halanges of these digits.

The arrangement of the synovial sheaths is of some considerable clinical mportance, as it is obvious that deep septic inflammation involving the thumb jr little finger is more likely to spread upwards into the palm, and thence to he wrist and forearm, than it is in the case of one of the other digits.

Sheaths of the Flexor Tendons.—The two flexor tendons (superficial tnd deep) of each finger are contained in a fibro-osseous canal. The









492


A MANUAL OF ANATOMY


Flexor Profundus


Flexor

Sublimis


' _Vincula Longa


Vincula - Brevia


— Vincula Longa


-Vincula Brevia


osseous wall is formed by the palmar aspects of the proximal and ini mediate phalanges, and the fibrous wall by an arched sheath. T sheath, over the greater parts of the proximal and intermedi phalanges, is thick and strong, and these parts of it are known

the digital vaginal ligaments. The fibres disposed transversely, and are attached to rough lateral margins of the palmar surfa of the phalangeal shafts. Opposite the joir in order not to interfere with the moveme: of flexion, the vaginal ligaments are replac by thin membranes, superadded to which ; obliquely decussating fibres. Each fib osseous canal is lined by synovial membra: which is reflected over the contained tendc in such a manner as to furnish a sepan investment for each. To certain bands of t synovial membrane reflected from the tendc which it invests to the wall of the fibro-ossec canal which it lines the name vincula tendini (Fig. 3°8) is given. They are of two kinds vincula brevia and vincula longa. The vinci brevia are two in number—one for the sup< ficial and one for the deep flexor tendc They are broad, laterally compressed, triangul bands which are thickened by the presence elastic fibres, and connect each tendon, clc to its insertion, with the distal end of t . phalanx proximal to that into which it inserted, the vincula longa, few and inconstant, are narrow ban

wmch pass between the tendons and the phalanges, or from one tend< to the other.

The Lumbricals (Fig. 295) are four tapering muscles which a connected with the deep flexor tendons~in the palm, and are disti guislied numerically, the most lateral being the first. The first ar second arise m each case from the outer side of the deep flexor tendc lor the index and.the middle finger respectively; the third and fourl ar ?? e , 1 T m y? e adjacent sides of the two deep flexor tendons betwee lle > the tendons concerned being those for the middle, rin : and little fingers. Each muscle tapers and ends distally in a tendc 1C roun( t the outer side of a metacarpo-phalangeal join

pan s and biends with the outer side of the broad expansion of tf xtensor tendon on the back of the proximal phalanx.

mus . c ^ es are embedded in loose connective tissue continuoi floor of the nalm lie ^ e ply to the flexor tendons, between them and tl

as the middle rTi ^ 1S ( L e ^ 1 1 1 ^ ar tissue occupies two spaces known respective! lyinsltendons thenar s P aces ' which are separated from the ove: septum The mid if^ 10118 m embrane, and from one another by a dense fibroi the connective 6 r s P ace has three distal diverticula prolonged int

e sheaths of the three inner lumbricals associated with tb


Fig. 308. —The Flexor Tendons of a Finger.






THE UPPER LIMB


493


ixor tendons of the little, ring, and middle fingers respectively. The thenar )mpartment is related superficially to the flexor tendons of the index finger id that of the flexor pollicis longus; it is similarly prolonged distally into the mnective tissue sheath of the first lumbrical muscle. The two spaces comunicate with one another proximally.

Nerve-supply .—The first and second are supplied by the median erve, the branches being derived from the third and fourth digital erves respectively (p. 489). The third and fourth are supplied by le deep division of the ulnar nerve.

The branches from the median nerve supplying the first and second lumbricals iter their superficial aspects; the branches of the ulnar nerve to the third and mrth enter their deep aspects. The nerve-supply of the second lumbrical is iconstant. It is sometimes supplied by the deep branch of the ulnar nerve, nd may have a double nerve-supply, a branch from the median entering its iperficial aspect, another from the ulnar entering its deep aspect.

Action .—Flex the metacarpo-phalangeal joints, and extend the iterphalangeal j oints.

The Flexor Retinaculum (Fig. 307) is a strong fibrous band which 'ridges over the concavity on the palmar aspect of the carpus, and onverts it into a fibro-osseous canal. Laterally it is attached to the ubercle of the scaphoid and trapezium; medially to the ridge on the •isiform and the hook of the hamate. Its upper border is continuous rith the deep fascia on the front of the forearm; its lower border is onnected with the palmar aponeurosis; at its upper and inner part it eceives an expansion from the tendon of the flexor carpi ulnaris; and he deep aspect of the tendon of the palmaris longus is attached to it. die retinaculum is crossed by the last-mentioned tendon and the ilnar vessels and nerve, the latter structures lying close to the pisiform >one, where they are overlapped by a slip from the tendon of the flexor arpi ulnaris. At either side the retinaculum affords origin to the short auscles of the thumb and of the little finger respectively. The fibro>sseous canal formed by the retinaculum and the anterior concavity of he carpus gives passage to the tendons of the flexors digitorum sublimis ind profundus, the tendon of the flexor pollicis longus, and the median ierve. Towards the outer side of the wrist a deep slip of the retinaculum s attached to the lip of the groove below the crest of the trapezium, nd with the main part of the retinaculum superficially converts the groove into a canal containing the tendon of the flexor carpi radialis, vhich may consequently be regarded as traversing the flexor retinaculum.

The Short Muscles of the Thumb—1. Abductor Pollicis Brevis

Fig. 305)— Origin .—The front of the flexor retinaculum; the tubercle )f the scaphoid; and the crest on the trapezium.

Insertion .—The outer side of the base of the proximal phalanx of he thumb, in common with flexor pollicis brevis, and the outer margin )f the tendon of the extensor pollicis longus on the back of the proximal phalanx.

Nerve-supply .—The median nerve.


494


A MANUAL OF ANATOMY


The muscle is triangular, and is directed downwards and oi wards.

Action. —Abducts the thumb and assists in flexing its proxirr phalanx, the result being that the thumb is drawn forwards and little inwards. It also assists in extending the distal phalanx.

The muscle is superficial, and lies on the opponens pollicis ai partially flexor pollicis brevis, a part of which appears on its inner sic

2. Opponens Pollicis (Fig. 309)— Origin. —The front of the flex retinaculum, and the crest on the trapezium.

Insertion. —The outer border of the shaft of the metacarpal bone the thumb, and the adjacent part of its palmar surface.

Nerve-supply. —The median nerve.

The muscle is triangular, consists of two or more laminae, and directed downwards and outwards.

Action. —Flexes the first metacarpal bone, the result being that tl thumb is drawn forwards and inwards across the palm, bringing it in a position in which its tip may be readily opposed to the tip of any oi of the four fingers.

The muscle is deep to the abductor pollicis brevis, the flexor pollic brevis lying along its inner border.

3. Flexor Pollicis Brevis (Fig. 309) arises from the outer two-thin of the lower border of the flexor retinaculum, and the crest on tl trapezium.

Insertion. —Ending in a tendon, it is inserted, in common with tl abductor pollicis brevis, into the outer side of the base of the proxim phalanx of the thumb. A sesamoid bone occupies the commc tendon of insertion opposite the metacarpo-phalangeal joint.

Nerve-supply. —A branch of the median nerve.

Action. —-Flexes the metacarpo-phalangeal joint of the thuml and thus assists in the movement of opposition of the thumb.

4. First Palmar Interosseous— Origin. —The inner aspect of tl proximal extremity of the first metacarpal bone.

Insertion. —It ends in a tendon which joins with those of tb oblique and transverse heads of adductor pollicis, with which it inserted into the inner side of the base of the proximal phalanx of tb thumb. A sesamoid bone is contained in the common tendon.

Nerye-supply. —Ihe deep division of the ulnar nerve.

Action. Assists in flexing the metacarpo-phalangeal joint of tb thumb.

5. Adductor Pollicis (Fig. 309) consists of two fleshy heads, obliqu

and transverse.

Oblique Head— Origin. —By several slips from the bases of th second and third metacarpal bones; the trapezoid and capitate; and tb sheath of the tendon of the flexor carpi radialis.

Insertion. The muscle is inserted with the first palmar interosseou and the transverse head into the inner side of the base of the proximo phalanx of the thumb.

A large fleshy slip from the outer side of the muscle passes outwarc


THE UPPER LIMB


495


eply to the tendon of the flexor pollicis longus, and joins the flexor llicis brevis.


'• 309. The Insertions of the Long Flexor Tendons and the Short Muscles of the Thumb and Index Finger.

e abductor of the thumb and of the little finger has in each case been partially removed. On the middle finger the flexor sheath (vaginal ligament) is shown ; on the little finger are the two long flexor tendons; on the ring finger is the tendon of the flex. dig. subl., that of the flex. dig. prof, having been removed; on the index finger is the tendon of the flex. dig. prof., the tendon of the flex. dig. subl. having been removed.


Nerve-supply .—The deep division of the ulnar nerve. The muscle is directed downwards and outwards.















496


A MANUAL OF ANATOMY


Action. —Adducts the thumb and assists in the movement opposition.

The muscle has the flexor pollicis brevis on its outer side, t tendon of the flexor pollicis longus lying between the two; the trai verse head occupies its inner and lower border, the deep palmar ai passing between the two.

Transverse Head (Fig. 309)— Origin. —The distal two-thirds of t anterior border of the shaft of the third metacarpal bone.

Insertion .—The inner side of the base of the proximal phalanx the thumb, in common with the oblique head and the first pain] interosseous; and the inner margin of the tendon of the extensor polli longus on the back of the proximal phalanx.

Nerve-supply .-—The deep division of the ulnar nerve.

The muscle is triangular, and is directed outwards.

Action .—Adducts the thumb and assists in the movement opposition. It also assists in extending the distal phalanx.

The tendon of the flexor pollicis longus crosses the tendon of t flexor carpi radialis at the wrist, and in the palm lies between t flexor pollicis brevis on its outer side and the oblique head of adduct pollicis on its inner side.

The Short Muscles of the Little Finger—1. Abductor Digiti Mini]

(Fig. 309)— Origin. —The lower part of the pisiform bone.

Insertion .—The inner side of the base of the proximal phalanx the little finger, in common with the flexor digiti minimi; and the inn margin of the expansion of the extensor tendon on the back of t phalanx.

Nerve-supply. —The deep division of the ulnar nerve.

Action. —Adducts the little finger, flexes its metacarpo-phalange joint, and assists in extending its intermediate and distal phalanges.

2. Flexor Digiti Minimi (Fig. 309)— Origin. —The inner surface the hook of the hamate bone close to its tip, and the front of tl adjacent portion of the flexor retinaculum.

Insertion .—The inner side of the base of the proximal phalanx of t] little finger, in common with the abductor digiti minimi.

N erve-supply. —The deep division of the ulnar nerve.

Action. —Flexes the metacarpo-phalangeal joint of the little finge

The muscle is small, and lies on the outer side of, and partially und cover of, the abductor digiti minimi, from which it is separated, clo co its origin, by the deep branch of the ulnar artery and the dec division of the ulnar nerve.

3. Opponens Digiti Minimi (Fig. 309)— Origin. —The inner surfa< of the hook of the hamate bone under cover of the preceding muscl and the adjacent part of the flexor retinaculum.

Insertion. The inner aspect of the shaft of the fifth metacarp; bone.

Nerve-supply. —The deep division of the ulnar nerve.

Action. Flexes and adducts the fifth metacarpal bone.

The muscle lies deeply to the abductor and flexor digiti minim


THE UPPER LIMB


497


id its deep surface is in relation with the interosseous muscles of Le fourth interspace. The deep branches of the ulnar artery and of le ulnar nerve may pass through it on their way to the deep part of le palm.

The Third Part of the Radial Artery (Fig. 310) forms the greater Drtion of the deep palmar arch, and extends inwards from the proximal id of the first intermetacarpal space to join the deep branch of the nar artery. It enters the palm by passing forwards between the vo heads of the first dorsal interosseous muscle and crosses the floor

the palm, lying upon the bases of the second, third, and fourth


[g. 310.—The Deep Palmar Arch and the Deep Branch of the Ulnar Nerve, together with the Muscular Structures occupying the Floor of the Palm.

metacarpal bones and the adjacent interosseous muscles. Towards ie outer side of the palm it lies deeply to the oblique head of adductor ollicis, but emerging between this head and the transverse head, it lies eeply to the flexor tendons and lumbrical muscles towards the inner de of the palm. The deep palmar arch describes a slight curve with ie convexity directed towards the fingers, and is about 1 inch nearer ie wrist than the superficial palmar arch. The deep division of the lnar nerve lies in front of it.

Branches of the Deep Palmar Arch.—The princeps pollicis artery

rises from the outer extremity of the arch, and passes downwards

32











A MANUAL OF ANATOMY


498

between the two heads of adductor pollicis superficially and the fi dorsal interosseous muscle deeply. At the distal end of the fi metacarpal bone, and on the deep aspect of the tendon of the fie: pollicis longus, it divides into two collateral branches which are c tributed to either side of the thumb.

The radialis indicis artery passes downwards on the outer side the second metacarpal bone, lying on the first dorsal interosseous, a deeply to both heads of adductor pollicis; it is finally distributed to 1 outer side of the index finger.

The princeps pollicis and radialis indicis arteries not infrequently arise a common trunk. The final distribution of the two arteries is similar to t] of a digital branch of the superficial palmar arch.

The three palmar metacarpal arteries arise from the convexity the arch, and pass downwards in the second, third, and fourth int metacarpal spaces lying upon and supplying the interosseous muscl They terminate by joining the digital arteries of the superficial palm arch, meeting these vessels just before they subdivide into th collateral branches. The innermost palmar metacarpal artery usual gives off a communicating branch, which joins the digital artery frc the superficial arch supplying the inner side of the little finger.

When the digital arteries from the superficial arch are deficient, the pain metacarpal arteries may take their place in supplying blood to the fingers.

The recurrent branches, few and small, pass upwards and ta part in forming the anterior carpal rete.

The three perforating arteries pass backwards through the proxim ends of the inner three intermetacarpal spaces and between the t\ heads of the corresponding dorsal interosseous muscles. On the ba of the hand they join the dorsal metacarpal arteries.

Varieties of the Ulnar and Radial Arteries in the Hand—The Ulnar Artery.

The digital branches furnished by the superficial palmar arch may be deficiei or the ulnar artery may end in the deep palmar branch, in which case the sup< ficial arch is absent. Under these circumstances the digital arteries are usua' derived from the palmar metacarpal branches of the deep arch. In some ca^ a large median together with a large superficial palmar branch furnish the digil arteries.

The Radial Artery ,—The princeps pollicis and radialis indicis arteries, norma] arising from the radial, may be derived from the superficial arch, from an enlarge median artery, or from the superficial palmar branch.

Veins.— The deep palmar arch is accompanied by two small ven comites which receive tributaries corresponding to the branches of tl arch.

Summary of the Palmar Arches .—The superficial palmar arch is form

mainly by the ulnar artery, and is completed by the superficial palmar bran of the radial, or, failing this, by a branch from the radialis indicis artery, or frc the princeps pollicis artery, its digital branches corresponding in position

! 5 t ? rmetaCarpa l s P aces - I 11 order to avoid them, incisions in the pal should be made in line with the middle line of a finger, and should not be pi longed farther upwards than the line indicating the position of the superfic:|


1

I


I'


THE UPPER LIMB


499


lmar arch. On the fingers the digital arteries are placed laterally, conseently in cases of whitlow the incision should be made along the middle line a finger.

The deep palmar arch is formed mainly by the radial artery, and is combed by the deep branch of the ulnar. It lies about i inch proximal to the perficial arch.

The Ulnar Nerve (Fig. 310) gains the hand by passing superficially the flexor retinaculum, where it lies on the inner side of the ulnar

ssels, and is overhung by the pisiform bone. More distally it lies l the piso-hamate ligament, and grooves the inner aspect of the hook the hamate bone. It subdivides into two divisions—superficial id deep. The superficial division passes downwards deeply to the ilmaris brevis, to which it gives a branch, and ends by dividing into 10 digital nerves. One is distributed to the inner side of the little lger. The other divides into two collateral digital nerves for the pply of the adjacent sides of the little and ring fingers. This nerve •mmunicates with the innermost digital branch of the median. The stribution of the nerves on the fingers corresponds with that of the edian palmar branches; they supply the joints as well as the skin, id furnish dorsal branches to the backs of the fingers. The deep vision accompanies the deep branch of the ulnar artery, passes be/een the abductor and flexor digiti minimi, and through, or deeply to, Le opponens digiti minimi. Gaining the floor of the palm, it accommies the deep palmar arch, in front of which it lies. It has an Tensive muscular distribution, supplying the abductor, flexor, and )ponens digiti minimi, the inner two lumbricals, the eight interossei, id one thumb muscle—namely, the two heads of adductor pollicis. also gives articular twigs to the wrist-joints and to the metacarpolalangeal joints.

Summary of the Ulnar Nerve—Muscular. —In the forearm it supplies the xor carpi ulnaris and inner part of the flexor digitorum profundus; in the hand supplies the palmaris brevis, the three short muscles of the little finger, the tier two lumbricals, the eight interossei, and one thumb muscle—namely, ith heads of adductor pollicis. Cutaneous. —It supplies the skin of the front the forearm for a variable extent, the inner part of the palm, and the inner te and a half fingers. Articular. —It supplies branches to the elbow- and wristints and several of the joints of the hand.


Back of the Forearm and Hand.

The skin on the outer side of the back of the forearm is supplied Y the posterior branch of the lateral cutaneous nerve of forearm, fat on the inner side by the posterior branch of the medial cutaneous forearm. Between the two, and occupying a more central position, the posterior cutaneous nerve of forearm.

Muscles on the Back of the Forearm. —The muscles exposed to ew (Fig. 312) when the skin and fascial layers are removed from the ick of the forearm are disposed as follows:

To the inner side of the posterior subcutaneous border of the ulna


5°°


A MANUAL OF ANATOMY


Brachialis


Brachioradialis


E.C. Rad. Long.


E.C. Rad. Brevis


Common Extensor


is the flexor carpi ulnaris, which, although it is a flexor muscle a was described with the muscles on the front of the forearm, occup the back of the limb to a considerable extent.

The extensor muscles proper are all disposed to the outer side the posterior border of the ulna, and are arranged in the followi groups:

1. A small triangular muscle, t anconeus, is confined to the region the elbow.

2. An outer marginal group three muscles, in order from withe inwards—the brachio-radialis, exte sor carpi radialis longus, and extern carpi radialis brevis—occupy the oul aspect of the limb.

3. An inner group of three exte sor muscles which, as a group, folk the posterior border of the ulna; t extensor digitorum, extensor dig minimi, and extensor carpi ulnaris in this order from without inwards.

4. In the upper part of the foi arm groups 2 and 3 are in juxt position, but towards the lower pa they diverge from one another, ai in an elongated angular interval b tween them there appear three muscl of the thumb—the abductor pollic longus, extensor pollicis brevis, ar extensor pollicis longus, in this ord from above downwards. The thr muscles are for the most part on deep plane, but, outcropping as were between the two superfici groups, incline obliquely down wan and outwards to reach the thum and cross the lower ends of thri outer marginal muscles superficial before attaining their destination They will be described with the dee extensor muscles.

1. Anconeus (Fig. 312)— Origin.The back of the lateral epicondyle < the humerus.

Insertion. The outer surface of the olecranon process, and tl upper third of the posterior surface of the shaft of the ulna, its attacl merit being limited below by the oblique line on the bone.

the muscle is triangular, the upper fibres being short and tran:


Abd. Poll. Long.


E. Poll. Brevis


Poll. Longus


Fig. 311. Muscles on Lateral Aspect of Forearm.




THE UPPER LIMB


501

tersely disposed, whilst the lower fibres pass obliquely downwards tnd inwards.

Nerve-supply .—A branch of the radial nerve, which is chiefly

oncerned in supplying the medial head of the triceps (p. 461). Action .—Assists the triceps in extending the elbow-joint.

The posterior interosseous recurrent artery ascends under cover )f the muscle to the back of the lateral epicondyle.

The anconeus is frequently inseparable from the medial head of the triceps, 'he muscle may be regarded as a part of the triceps displaced downwards into he forearm.

2. Outer Marginal Group—Brachio-radialis (Fig. 312)— Origin .— fhe upper two-thirds of the lateral supracondylar ridge of the humerus, nd the front of the lateral intermuscular septum to a corresponding xtent.

Insertion .—The outer side of the lower end of the radius some little listance above the styloid process, chiefly to the floor of the upper nd of the groove lodging the tendon of the abductor pollicis longus, n the deep aspect of which the insertion lies.

Nerve-supply .—The radial nerve.

Action .—The muscle is mainly a flexor of the forearm, acting most ffectively when the limb is in a state of semipronation. An important Lse of the muscle is to maintain the forearm in the flexed position, as ti holding a book. When the forearm is fully pronated the muscle 3 a feeble supinator, bringing the limb to a position midway between omplete pronation and complete supination, but only to the extent f semisupination. On the other hand, when the forearm is fully upinated, it can act as a pronator, again bringing the limb into the ntermediate position.

Above the muscle has a fleshy belly, which towards the lower part f the forearm is replaced by a flat tendon, first appearing on the Leep surface of the muscle. In the arm the muscle belly is flattened rom side to side, but in the region of the elbow it is twisted upon tself in such a way that in the forearm it is flattened from before »ack wards.

Extensor Carpi Radialis Longus— Origin .—The lower third of the iteral supracondylar ridge of the humerus, and the front of the lateral ntermuscular septum to a corresponding extent.

Insertion .—The outer part of the base of the second metacarpal >one, a small bursa underlying the tendon at its insertion.

Nerve-supply .—The radial nerve.

Action .—Extends and assists in abducting the wrist-joint.

The relatively small muscle belly ends in the lower part of the orearm in a tendon which descends at first superficially to, and at lower level on the outer side of, the tendon of the extensor carpi adialis brevis. The two tendons pass deeply to the extensor retinculum, and occupy the outermost groove on the back of the lower nd of the radius.


=>02


A MANUAL OF ANATOMY


Extensor Carpi Radialis Brevis (Fig. 312)— Origin .—The lal epicondyle of the humerus; the lateral ligament of the elbow-jc and the intermuscular septa between it and the adjacent muscles. Insertion .—The outer part of the base of the third metaca

bone, and often by a small sli


the base of the second metacar A small bursa underlies the ten at its insertion.

Nerve - supply .—The de branch of the radial nerve.

Action .—Extends and ass in abducting the wrist-joint.

The tendon appears about middle of the forearm, and comes free from fleshy fibres in lower third. It descends dee to the tendon of the long ra< extensor, except near its inserti where it lies internal to it. accompanies the long ten< under cover of the extensor rel aculum, and passes with it throi the outermost groove on the b; of the lower end of the radius.

3. The Inner Group of Extens all arise by a common tenc from the lateral epicondyle of humerus.

Extensor Digitorum (Fig. 3 — Origin .—The lateral epicond of the humerus; the deep fasc and the intermuscular septa tween it and adjacent muscles.

Insertion .—The muscle ends four tendons, the innermost which does not attain its in pendence until the back of 1 hand is attained. The tend( pass deeply to the extensor ret aculum, where they occupy 1


Fig. 3i2.—The Muscles on the Back wnere ™ey 0CCU PY

of the Forearm exposed when broacl innermost groove on the Skin and Fascial Layers are back of the lower end of removed. radius, and diverge from

another on reaching the b e arrangement of the tendons on the back of the hand is s< what variable, but is. usually as follows: The two outer tendons pro onge on to the index finger and the middle finger respect! Between the two tendons, and connecting them together, is an adhe














THE UPPER LIMB


503


lickened band of the deep fascia (vinculum), consisting of more or ss transversely disposed fibres. The tendon to the index finger ends with the tendon of the extensor indicis, which is disposed on its ner (ulnar) side. The two inner tendons in each case split into two, le two bands of the one passing to the middle and ring fingers, those

the other to the ring and little fingers. The band to the middle iger blends with the main tendon to that digit; the band to the little iger blends with the tendon of the extensor digiti minimi. The bands om the two inner tendons passing to the ring finger blend to form le extensor tendon of that digit.

From the arrangement of their tendons and from the fact that they are •ovided with special extending muscles, it follows that of the four fingers the dex and little are endowed with the greatest mobility as far as independent Tension is concerned, while the possibility of extending the ring finger indejndently is extremely limited.

On the dorsal aspect of the proximal phalanx the extensor tendon idens (extensor expansion) , and is here joined by the tendons of the imbrical and interosseous muscles. Towards the distal end of the roximal phalanx the tendon contracts, and, passing across the proximal fierphalangeal joint, the central part is inserted into the base of the dermediate phalanx. The lateral parts converge, and blending toother on the back of the intermediate phalanx, form a single tendon, hich is inserted into the base of the terminal phalanx.

IV erve-supply . —The posterior interosseous nerve.

Action. —Extends the distal phalanges on the proximal, the proximal halanges on the metacarpal bones, and the hand on the forearm.

Extensor Digiti Minimi (Fig. 312)— Origin. —The lateral epicondyle f the humerus; the deep fascia; and the intermuscular septa on either de of it.

In many cases the muscle, which is very narrow, does not extend upwards > high as the lateral epicondyle, but arises from the deep fascia and the interluscular septa only.

Insertion. —Its tendon passes deeply to the extensor retinaculum, here it occupies a groove between the radius and ulna. On the back f the hand the tendon splits into two, which reunite at the distal end f the fifth metacarpal bone, where it is joined by a slip from the mermost tendon of the extensor digitorum. The final insertion is imilar to that of a digital extensor tendon described above.

Nerve-supply. —The posterior interosseous nerve.

Action. —In addition to extending the little finger, it aids to some light extent in extending the wrist-joint.

Extensor Carpi Ulnaris — Origin. —The lateral epicondyle of the umerus, the deep fascia covering it, and by its means has an indirect ttachment to the posterior border of the ulna (cf. flex. carp, uln., '• 473) i the intermuscular septum on its outer side; some of its fibres re directly attached to the oblique line of the ulna, marking the lower unit of the attachment of the anconeus.


504


A MANUAL OF ANATOMY


Insertion. — The tuber


on the inner side of the b; of the fifth metacarpal bo:

Nerve-supply .—The p terior interosseous nerve.

Action. — Extends 1 wrist-joint, and assists


adducting the hand.

The muscle rests upon 1 inner half of the poster surface of the shaft of 1 ulna, and its tendon pas; deeply to the extensor ret: aculum, where it occupies groove on the back of t lower end of the ulna.

The Deep Muscles on t Back of the Forearm (F 313) are five in number, addition to the three thur muscles, which, in the low part of the forearm, outer between the two chief sup( ficial groups (p. 500), th include the supinator sit ated in the region of t elbow above the thur muscles, and below them t extensor indicis occupyi: the lower part of the foi arm, where it lies deeply the extensor digitorum. T five deep muscles have o: feature in common, in th they all incline oblique downwards and outwar from their origins to the insertions.

Supinator (Fig. 313) • Origin .—The muscle has long and continuous orig from the humerus abov where it arises from t] lateral epicondyle, to the uli below, where it is attach* to the supinator crest (a co


S P* 9 UC ^ S ^idge on the outer aspect of the bone, continuous abo with the hinder lip of the radial notch), and to some extent to tl













THE UPPER LIMB


505


epressed area of bone in front of it. Between the two bones the muscle rises from the lateral and orbicular ligaments occupying the outer spect of the elbow-joint. Some of its fibres are attached to a dense iscia covering its posterior surface.

Insertion .—The upper part of the shaft of the radius on its anterior, uter, and posterior aspects, occupying an area on the bone limited elow by the anterior and posterior oblique lines.

Nerve-supply. —The posterior interosseous nerve.

Action. —Supinates the radius upon the ulna.

The fibres of the muscle are, for the most part, spirally disposed, nd wind round the outer side of the radius from its posterior to its ntenor aspect. The muscle almost completely surrounds the upper tid of the radius and consists of two laminae, superficial and deep, the osterior interosseous nerve lying between them.

Abductor Pollicis Longus (Fig. 313)— Origin. —The posterior surface f the shaft of the radius for fully 2 inches below the posterior oblique ne; the adjacent portion of the interosseous membrane; and the outer art of the posterior surface of the shaft of the ulna for a short distance elow the oblique line which marks the lower limit of the insertion of he anconeus.

Insertion .—The outer side of the base of the metacarpal bone of he thumb.

The muscle passes obliquely downwards and outwards; its welllarked tendon crosses the insertion of the brachio-radialis, and is losely accompanied by that of the extensor pollicis brevis. Both mdons cross those of the radial extensors of the wrist superficially, nd occupy the groove on the outer side of the lower end of the radius, here they lie deeply to the extensor retinaculum.

Nerve-supply .—The posterior interosseous nerve.

Action. —Extends and abducts the metacarpal bone of the thumb, nd abducts the wrist-joint.

The tendon of the abductor pollicis longus is rarely single, and is usually mltiple, when it may consist of two or three tendons. Of these, one may be ttached to the trapezium, where it is usually associated with the attachment f the abductor pollicis brevis, the fibres of which may arise from it. Occasionlly the proximal end of the abductor pollicis brevis is not attached to bone, but ' directly continuous with the tendon of the abductor pollicis longus. This mdency to complexity and subdivision is a human characteristic, and probably idicates an increasing specialization of the movements of the thumb. It may ortend a numerical increase of the thumb musculature.

Extensor Pollicis Brevis (Fig. 313)— Origin. —The posterior surface f the shaft of the radius for a short distance below the preceding luscle, and the adjacent part of the interosseous membrane.

Insertion .—The back of the base of the proximal phalanx of the humb.

The muscle closely accompanies the abductor pollicis longus.

Nerve-supply. —The posterior interosseous nerve.

Action. —Extends the metacarpo-phalangeal joint of the thumb.

Extensor Pollicis Longus (Fig. 313)— Origin. —The outer part of


A MANUAL OF ANATOMY


506

the posterior surface of the shaft of the ulna for about its middle thin immediately below the attachment of the abductor pollicis longus, an the adjacent part of the interosseous membrane.

Insertion .—The back of the base of the distal phalanx of the thuml

The muscle is directed obliquely downwards and outwards; ii tendon passes deeply to the extensor retinaculum, where it occupi( the narrow oblique groove on the radius, medial to the dorsal tubercL

N'ewe-supply .—The posterior interosseous nerve.

Action .—Extends the distal phalanx of the thumb. Further cor traction assists in extending the proximal phalanx and also the mete carpal bone.

Extensor Indicis (Fig. 313)— Origin .—The outer part of the posteric surface of the shaft of the ulna, below the attachment of the extensc pollicis longus, and the lower part of the interosseous membrane.

Insertion .—The inner side of the tendon of the common extensc to the index finger, which it joins at the level of the metacarpo-phalar geal joint.

The muscle is directed downwards and outwards, and its tendo lies deeply to the extensor retinaculum, where it occupies the innermoj groove on the back of the radius, in company with the commo extensor tendons, under cover of which it lies.

Nerve-supply .—The posterior interosseous nerve.

Action .—The muscle is the special extensor of the index finger.

The Posterior Interosseous Nerve (Fig. 313) is a branch of the radia its fibres being derived from the sixth, seventh, and eighth cervia nerves. It descends for a short distance deeply to the brachio-radiali: and then winds round the outer side of the upper end of the radiu: As it does so, it passes through the supinator, occupying the plan between the two layers of the muscle. It appears on the back of th limb from under cover of the superficial layer of the supinator, an descends for a short distance, lying on the deep layer. At the lowe edge of the supinator it comes into relation with the posterior intei osseous artery, with which it descends, the artery lying to its inne side, between the superficial and deep muscles on the back of th forearm.

Branches. —Before traversing the supinator, it supplies branche to the extensor carpi radialis brevis and to the supinator. As it passe through the supinator, it supplies further branches to this muscle At its escape from the supinator three short branches are given of and are distributed to the extensor carpi ulnaris, extensor digii minimi, and extensor digitorum. At a little lower level it gives 0: two long branches: one from its outer side supplies the abductor pollici longus, and ends in the extensor pollicis brevis; the other from,it inner side supplies the extensor pollicis longus, and ends in the extenso indicis. All these branches are given off in the upper part of th forearm. The nerve is now reduced to a very slender trunk, to whic. the name posterior interosseous can be more properly applied. I descends between the superficial and deep extensor muscles, a mor


THE UPPER LIMB


507


• less close companion of the posterior interosseous artery. Reaching le upper border of the extensor pollicis longus, it descends deeply > this muscle, and lies directly on the interosseous membrane. Finally, passes on to the back of the radius, and lies in the groove containing le tendons of the extensor digitorum and extensor indicis, together


Pig. 314. —The Extensor Tendons on the Dorsum of the Hand.


dth the terminal part of the anterior interosseous artery. It ends ere in a gangliform enlargement, which is prolonged downwards on to he back of the wrist, and from which branches are distributed to the uist and carpal joints.

The Posterior Interosseous Artery passes backwards tnrough an iterval between the upper border of the interosseous membrane and





5°8


A MANUAL OF ANATOMY


the oblique cord. At the back of the forearm it appears between t supinator and abductor pollicis longus, where it is joined by t posterior interosseous nerve. The artery and nerve descend betwe the superficial and deep extensor muscles to the upper border of t extensor pollicis longus. Here the artery leaves the nerve, and pas< superficially to this muscle and to the extensor indicis. At the lov border of the latter muscle it anastomoses with the posterior termii branch of the anterior interosseous, and usually ends by supplying t wrist-joint. It may join the posterior carpal arch.

Branches .—The posterior interosseous recurrent arises at the lov border of the supinator, and passes upwards between this muscle a


the anconeus to the back of the lateral epicondyle, where it anash mosesi with the posterior branch of the profunda of the brachial. Sma u 0S r ^ mif y on the back of the olecranon process and, anastomosis y 1 . °f fhe posterior ulnar recurrent, form the olecranon ret

in addition it anastomoses with the muscular branches of the rad h recurren . M.uscular branches from the trunk of the posterior intei osseous supply the extensor muscles on the back of the forearn Articular branches supply the wrist-joint.

The Extensor Retinaculum is a thickened portion of the deep fasci e i 3ac " /he fore arm. It is attached laterally to a bony cres a le ower end of the radius, marking the outer limit of the attach









THE UPPER LIMB


509


lent of the pronator quadratus, and medially to the inner and back ►art of the triquetral and pisiform bones; it is here continuous with he fibres of the flexor retinaculum. Its general direction is obliquely ownwards and inwards from the outer side of the lower end of the adius to the inner side of the carpus. It bridges over the various rooves on the dorsal aspects of the lower ends of the radius and ulna, nd being attached by deep processes to the ridges between them, conerts them into fibro-osseous canals in which the extensor tendons are ontained. These canals are six in number and, rom without inwards, are disposed as follows:

'he first corresponds with the groove on the uter side of the lower end of the radius, and ontains the tendons of the abductor pollicis Dngus and extensor pollicis brevis. The second orresponds with the broad groove to the inner ide of the styloid process, and contains the endons of the extensor carpi radialis longus nd extensor carpi radialis brevis. The third orresponds with the narrow, deep, oblique roove on the back of the radius medial to the lorsal tubercle, and contains the tendon of he extensor pollicis longus. The fourth correponds with the broad, innermost groove on he back of the radius, and transmits the endons of the extensor digitorum and extensor adicis, together with the posterior interosseous ierve, which is here expanding into a pseudoanglion, and the terminal branch of the nterior interosseous artery. The fifth correponds with the groove between the radius nd ulna, and contains the tendon of the xtensor digiti minimi. The sixth corresponds dth the groove on the back of the ulna •etween the styloid process and head of the •one; it transmits the tendon of the extensor arpi ulnaris. Each canal is lined by a separate ynovial sheath, the sheaths extending for ome distance above and below the extensor etinaculum (Fig. 315).

The Deep Fascia of the Back of the Hand. —The deep fascia in this sgion is continuous above with the extensor retinaculum, and at ither side with the thenar and hypothenar portions of the palmar iscia. It covers the extensor tendons, with which it is intimately onnected. A deeper fascial layer lies under cover of the extensor sndons; it invests the dorsal interosseous muscles, and is attached 3 the metacarpal bones between them.

The Second Part of the Radial Artery (Fig. 317) winds backwards elow the styloid process of the radius to the back of the wrist. On





5 IQ


A MANUAL OF ANATOMY


the back of the wrist it extends downwards to the proximal end of t first intermetacarpal space, where it passes forwards between the t\ heads of the first dorsal interosseous muscle, and thus gains the pain Relations — Superficial .—The skin, the commencement of the rad: vein, branches of the radial nerve, the tendons of the abductor polli< longus, extensor pollicis brevis, and extensor pollicis longus; the la


ITg. 317. —The Arteries on the Back of the Hand.

The small vessels supplying the dorsal segments of the digits are derived fro

the palmar digital arteries.

named crosses the vessel just before it disappears between the two heac of the first dorsal interosseous. At first it is deeply placed, but at tl back of the wrist it is comparatively superficial. In the living subje< its pulsation may be detected in a triangular depression bounded c the outer side by the tendons of the abductor pollicis longus an extensor pollicis brevis, on the inner side by the tendon of the extens<













THE UPPER LIMB


5 ii

ollicis longus (p. 484). Deep .—The lateral ligament of the wrist-joint, tie scaphoid and trapezium, and the ligaments connecting them Dgether. The artery is accompanied by two venae comites.

Branches.—The posterior carpal branch arises from the radial as it es upon the lateral ligament of the wrist-joint. It passes inwards on tie back of the wrist deeply to the extensor tendons, and joins the poserior carpal branch of the ulnar artery to form the posterior carpal arch.

The first dorsal metacarpal artery is variable in origin, and arises ither directly from the radial or from the posterior carpal arch. It xtends downwards in tie second intermetaarpal space, lying on, nd supplying, the scond dorsal interossous muscle. At the roximal end of the pace it is joined by a perforating artery from tie deep palmar arch, t ends by dividing into wo dorsal collateral igital arteries which apply the adjacent des of the index and liddle fingers.

The second and third or sal metacarpal arteries re branches of the osterior carpal arch, nd occupy the third nd fourth intermetaarpal spaces respecvely. Their course nd distribution are .milar to that of the rst dorsal metacarpal; tie second is distributed i the adjoining sides of the middle and ring fingers; the third to the djoining sides of the ring and little fingers. A dorsal digital artery, applying the inner side of the little finger, arises either from the third orsal metacarpal artery or from the posterior carpal arch.

The dorsales pollicis are two small arteries which arise independently r by a common trunk from the radial opposite the base of the first letacarpal bone, and are distributed to either side of the thumb.

The dorsalis indicis artery arises a short distance above the point t which the radial passes forwards between the two heads of the first orsal interosseous. It descends on the outer side of the second metaarpal bone, and supplies the outer side of the index finger.


Fig. 318. —The Four Palmar Interosseous Muscles of the Right Hand.





5 12


A MANUAL OF ANATOMY


The dorsal digital arteries do not extend, as a rule, beyond the le\ of the proximal interphalangeal joint.

The Interosseous Muscles, eight in number, occupy the internet carpal spaces, and are arranged in two groups—four palmar and fo dorsal.

The four palmar interossei (Fig. 318), termed numerically, fro without inwards, the first, second, third, and fourth, occupy fo intermetacarpal spaces, and are inserted into the thumb, index, rin and little fingers. Each one of the four muscles arises from one met carpal bone only, and that one the metacarpal bone of the digit in

which the muscle is inserted. T


first palmar interosseous has ; ready been described with t] short muscles of the thumb (s p. 494); the remaining three w now be considered. The seco'i arises from the inner aspect of t] shaft of the second metacarp bone, and the third and four from the outer aspects of t] shafts of the fourth and fit metacarpals. The second is i serted partly into the inner si< of the base of the proximal phalai of the index finger, and part blends with the extensor expansk on the dorsal aspect of the phalan The third and fourth are inserh in a similar manner to the rii and little fingers, but are attache to the outer side of the base the proximal phalanx.

The four dorsal interossei (Fi 319), termed numerically, fro without inwards, the first, secon third, and fourth, occupy the foi intermetacarpal spaces, and a: inserted into the index, middl and ring fingers, the middle finger being provided with two. Eac muscle arises by two heads from the adjoining sides of the shafts of tl two metacarpal bones between which it is placed, and always moi extensively from the bone belonging to the digit into which the muse is inserted. The fibres of each muscle end in a tendon, which inserted partly into the side of the base of the proximal phalanx an partly into the extensor expansion on the back of the phalanx. Tl first is the largest of the series. Its outer larger head arises from tl proximal half of the first metacarpal bone, and its inner smaller hea from the whole length of the outer aspect of the shaft of the secon


Fm. 319 .—The Dorsal Interosseous Muscles of the Right Hand.








THE UPPER LIMB


5i3


letacarpal. The first and second dorsal interosseous muscles are iserted into the outer sides of the bases of the proximal phalanges of le index and middle fingers respectively, the third and fourth into the mer sides of the bases of the proximal phalanges of the middle and ng fingers.

Nerve-supply .—All the interossei are supplied by the deep division

the ulnar nerve. Action .—The palmar interossei are adductors of the index, ring, and ttle fingers. The dorsal interossei are abductors of the index, middle, id ring fingers.

The terms adduction and abduction are here used in reference to an imaginary le, corresponding to the axis of the middle finger, and which may be regarded

the physiological axis of the hand. It is towards and away from this line iat the fingers are naturally drawn when closing and opening the hand, the lgers closing in the former case and separating in the latter. As the thumb not only provided with its own special adductors, but with the first palmar terosseous, and the middle or axial finger requires no muscle to draw it towards 3 o\tn line, the three digits provided with the closing muscles or palmar intersei are the index, ring, and little fingers. As the two marginal digits, the Lumb and the little finger, are provided with special abducting muscles,’ the

ree digits provided with the separating muscles or dorsal interossei are the dex, middle, and ring fingers, the middle being provided with two, whereby it ay be made to diverge from its own axial line, either inwards or outwards.

Between the two heads of the first dorsal interosseous is an interval r the passage of the radial vessels, and between the two heads of the her three dorsal interossei is an interval for the passage of a perforating

tery connecting the deep palmar arch with a dorsal metacarpal tery.


Lymphatic Vessels of the Upper Limb.

The lymphatic vessels of the upper limb are arranged in two groups—superlal and deep. The superficial lymphatics lie in the subcutaneous tissue, and e mam vessels accompany the superficial veins; the deep lymphatics accomny the deep bloodvessels.

Superficial Lymphatics (Fig. 320)— Digital .—There are very rich networks of mphatics in the fingers, especially over their palmar aspects. The efferent nphatics from the digital networks are two digital vessels, one on either side a finger, accompanying the corresponding digital artery. At the roots of the f rs t ^ ese vessels pass to the dorsal aspect of the hand, and, communicating th each other, form a dorsal network, which is prolonged upwards on to the ck of the wrist.

Palmar. —There is a very rich network of lymphatics in the palm, from nch the lymph is collected by several vessels passing in various directions— wards, inwards, downwards, and upwards. The lateral efferent vessels pass wards and outwards over the thenar eminence, and join the lymphatics from e g 111 ^ 5, The m ediul efferent vessels pass inwards, and, winding round the ler border of the hand, join the lymphatics from the little finger. The inferior erent lymphatics pass down wards to the clefts between the fingers, where e y turn backwards and join the digital efferent lymphatics. The superior erent vessels ascend to the front of the wrist.

La fpal. —The carpal lymphatics are disposed in two groups—palmar and

rsa , the vessels of which are continuous with the palmar and dorsal networks the hand.


33


514


A MANUAL OF ANATOMY


Antibrachial. —The superficial lymphatics of the front of the forearm arranged in three groups—radial, median, and ulnar, which accompany corresponding veins. As the radial and ulnar lymphatics ascend they

joined at intervals by efferent vessels from the dc plexus of the hand, which wind round the radial ulnar borders of the forearm from its dorsal asf The radial lymphatics in part ascend into the < and accompany the cephalic vein, and in part the median lymphatics. The median lymphatics : terminate in the antecubital glands, should the present. When they are absent, they join the u lymphatics, which end in the supratrochlear g. or glands.

Brachial. — The superficial lymphatics of brachial region are disposed in two groups—ii and outer. The inner lymphatics, which are ' numerous, lie along the inner border of the bi brachii in more or less close association with basilic vein. They largely represent the effe vessels of the supratrochlear gland or glands, the antecubital glands, when they are present, the upper part of the arm they traverse the c fascia, and join the lateral axillary glands, in £ ciation with the deep brachial lymphatics. outer lymphatics are reinforced by some of the n lymphatics, and lie on the outer side of the bi brachii, following the cephalic vein. They as< in the groove between the deltoid and pecto major muscles, and join finally the infraclavic glands; one or two of them may ascend in froi the clavicle, and end in the supraclavicular glan The Deep Lymphatics accompany the deep bl vessels, and are disposed in five groups—ra ulnar, anterior interosseous, posterior interosse and brachial. There are usually two lympl vessels in connection with each artery. Those companying the radial, ulnar, anterior interosse and brachial arteries occasionally traverse on two small deep lymphatic glands, which are s< times met with along the course of these arte The brachial lymphatics are formed by the unic the radial, ulnar, anterior interosseous, and post interosseous lymphatic vessels. About the mi of the arm they are joined by the efferent ve of the supratrochlear gland or glands, and higher level by lymphatic vessels accompanying profunda artery. They end in the lateral axi glands.

Summary of the Lymphatic Glands of the l Limb. —The lymphatic glands of the upper form two groups—superficial and deep.

The superficial glands include the medial

condylar or supratrochlear and possibly the < cubital glands, but these are inconstant.

The deep glands occupy the axillary space (p. 434). Minute lymp]


Fig. 320. — The Superficial Lymphatics of the Upper Limb (Anterior View).


glands are occasionally found in association with the lymphatic vessels w accompany the arteries of the forearm and the brachial artery. One or lymphatic glands may occupy the groove between the deltoid and pectf major muscles in the course of the cephalic vein.









THE UPPER LIMB


5i5


Morphology and Development of the Intrinsic Muscles of the Hand.

An account of the morphology and the developmental changes affecting the uscles of the hand can be equally applied to those of the foot, the only difference •ing in the names of the individual muscles.

The lumbrical muscles are specialized parts of the muscle (flex. prof. dig), th which their origins are associated, and are consequently derived from the ep flexor sheet on the ventral aspect of the forearm.

The interossei, together with the short muscles of the thumb and little finger, e derived from a ‘ generalized type/ modifications of which are found in all limals possessing hands with four or five digits. In the early developmental ages of the human hand this generalized type is represented almost in its tirety, and the ontogenetic transformations which its musculature undergoes obably recapitulate its phylogenv.

The generalized mammalian hand has three planes of short digital muscles. (a) A deep set of intermetacarpal muscles which occupy the intermetacarpal aces, and are confined in their attachments to the metacarpal bones. ( b ) An termediate set of double-bellied short flexors which arise in each case from e proximal part of a metacarpal bone, the two bellies being inserted one on

her side of the base of the proximal phalanx of the corresponding digit, (c) A perficial set of contrahentes (muscles closing or bringing the fingers together wards the axial line of the middle digit) which arise from the front of the carpus, )m which they diverge, and are inserted into the bases of the proximal phalanges, le deep vessels and nerve lie in a plane between the contrahentes superficially d the short flexors deeply.

A secondary modification affects the contrahentes muscles in that the conihens muscle of the middle finger, which can only act as a flexor, and is conquently superfluous, loses its muscle fibres and becomes modified into a fibrous rd along which the origins of the remaining muscles spread, and their adducting ect on the more marginal digits is thereby increased.

The Intermetacarpal and Short Flexor Muscles. —The radial belly of the -ond, both bellies of the third, and the ulnar belly of the fourth short flexor ik dorsalwards, and fuse with the intermetacarpal muscles, which thus

ondarily acquire an attachment to the proximal phalanges and form a group abducting muscles, the four dorsal interossei. The remaining bellies of the ort flexors, with the exception of the radial belly of the muscle of the thumb d the ulnar belly of that of the little finger, maintain their independence, d are represented by the four palmar interossei. They lose to a certain extent

sir primary function as flexors, and serve as adductors (secondary contrantes). v y

The contrahentes are nearly complete in the early human foetus, but to a ge extent disappear in the course of development, that of the thumb being e sole survivor. The proximal attachment of this muscle extends distally >ng the fibrous cord representing the contrahens muscle of the middle digit. [ls fibrous cord becomes implanted deeply on to the shaft of the third metarpal, except in the situation where it is held off by the deep artery. Thus s muscle which is represented by the adductors of the thumb is, in descriptive atomy, said to consist of two parts—the transverse head of adductor pollicis -ached to the third metacarpal distal to the artery, and the oblique head proximal end of the third metacarpal and to the carpus.

Thenar and Hypothenar Muscles. —For these muscles a marginal member of 3 intermetacarpal set of muscles occupying the free surface of each marginal flacarpal bone (thumb and little finger) must be postulated. The origin of 5 muscle extends proximally, and it forms a primary abductor. Later the eilC * the musc l e spreads towards the centre of the palm superficially the pMmar vessels and on to the flexor sheath (of the long flexor tendons), rt of this muscle splits off and forms a short flexor (flex. poll. brev. or flex.

mm ); the rest of the muscle maintains the original position, and persists tfle abductor proper (abd. poll. brev. or abd. dig. min.). From the marginal


A MANUAL OF ANATOMY


5i6

belly of the short flexor (of the thumb or little finger), which took no part in the formation of the interosseous muscles (vide supra), the opponens muscle is derived by the migration of its insertion from the proximal phalanx to the shaft of the metacarpal bone, and the extension of its origin on to the flexor sheath.

The opponens of the little finger, as a part -of the primitive short flexor of this digit, at first lies deeply to the deep artery and nerve. As its proximal end undergoes a secondary extension on to the ventral aspect of the limb, it grows round these structures, and its continuity is to some extent interrupted, the artery and nerve being said to pass through the muscle. Whether the primary part of the muscle persists or no, the position of the nerve always indicates the demarcation between the two parts of the muscle.

Development of Arteries of Upper Limbs.

The arterial stem of the left upper limb is developed entirely from the seventh left cervical segmental artery in association with the left vertebral artery. The component arteries of this stem, from above downwards, are as follows: (1) The subclavian artery; (2) the axillary artery; (3) the brachial artery; and (4) the anterior interosseous artery. The arterial stem of the right upper limb is developed from the fourth right arterial arch, a portion of the right dorsal aorta, and the seventh right cervical segmental artery, in association with the right vertebral artery. The component arteries of this stem are similar to those on the left side.

Before the adult condition of the arteries is reached, several stages of development have to be passed through.

(1) As the anterior interosseous artery becomes diminished, another artery springs from the brachial a short distance below the elbow-joint. This new vessel accompanies the median nerve, and is called the median artery.

(2) The median artery superiorly furnishes a branch, which becomes the

ulnar artery.

(3) As the median artery becomes diminished, a vessel springs from the brachial artery about the centre of the brachial region. This vessel is called the primary radial artery, and it accompanies the radial nerve.

(4) As the upper part of the primary radial artery atrophies, the brachial artery gives off another branch just below the elbow-joint, which soon joins the primary radial, and so the permanent radial artery is formed.

Development of Veins of Upper Limbs.

The veins of each upper limb form two groups—superficial and deep. The superficial veins are developed prior to the deep, the latter accompanying the arteries.

The primitive vein is the primary ulnar or postaxial vein, which receives distally the digital veins, and opens proximally into the anterior cardinal vein. At a later period the cephalic vein is formed as an outgrowth from the external jugular vein, but it subsequently acquires its permanent connection with the upper part of the axillary vein.

The distal portion of the primary ulnar vein disappears. Its proximal portion persists and gives rise to the basilic, axillary, and subclavian veins.

From the distal end of the basilic vein the anterior and posterior ulnar veins and the median basilic vein are developed.

The radial and median cephalic veins grow distally from the cephalic vein.

The median vein is developed from the median basilic and median cephalic veins.

The Elbow-Joint.

I he articular surfaces taking part in the formation of the joint are the trochlea and capitulum of the humerus above, and the trochlear notch of the ulna and the cup-shaped depression on the head of the


THE UPPER LIMB


517

radius below. The trochlea articulates with the trochlear notch, the capitulum of the humerus with the head of the radius. The joint is surrounded by a capsule, in which four ligaments—anterior, posterior, lateral, and medial—may be recognized.

The anterior ligament is broad, thin, and weak, the central portion being the strongest. Its fibres are attached above to the front of the humerus above the coronoid and radial fossae, and below to the coronoid process of the ulna and the annular ligament. Most of its fibres are vertical; some superficial fibres pass obliquely downwards


Tig. 321.—The Right Elbow-Joint (Anterior View).


and outwards. The ligament is closely covered in front by brachialis, which is, to a certain extent, adherent to it.

The posterior ligament is thin and membranous. Above it is attached to the margins of the olecranon fossa of the humerus, and below to the front part of the upper aspect of the olecranon process of the ulna and to the annular ligament of the radius. Most of its fibres are disposed vertically, but a few pass transversely between the margins of the olecranon fossa, especially in its upper part, where they are disposed as a band with an upper free edge, above which, between it and the upper part of the olecranon fossa, is a deficiency in the capsular ligament through which a pad ’of fat, invested by synovial membrane, protrudes when the elbow-joint is extended.








5i8


A MANUAL OF ANATOMY


Attention may be drawn to the fact that the coronoid fossa of the humeru is completely roofed by the capsular ligament, while the upper part of th< olecranon fossa is above the limits of the capsule.


The ligament is covered behind b} the tendon of insertion of the tricep: and the anconeus.


A few of the deep fibres of the inner heac of the triceps have been described (Theile as being attached to the posterior ligameni under the name of the subanconeus muscle.


Fig. 322.—The Posterior Ligament of the Elbow-Joint.


The lateral ligament is a thick triangular band, attached above to the lower part of the lateral epicondyle oi the humerus, and below to the annular ligament; some of its fibres may be traced to the bony ridges on the ulna, extending downwards from the anterior and posterior margins of the radial notch. The extensor carpi radialis brevis and supinator muscles are attached to it.


The medial ligament is triangular, with the apex upwards. It is attached above to the medial epicondyle of the humerus, and below to the inner margin of the trochlear notch of the ulna. It consists of three parts: An anterior, attached .aboveTo the front and lower part of the medial epicondyle, and


below to the inner margin of the coronoid process. A posterior, attached above to the lower and back part of the medial epicondyle, and below


ateral Ligament


Annular Ligament


to the inner margin of the


olecranon process. A middle, a comparatively weak part of the ligament, consists of fibres which are mainly attached to a fibrous band (oblique ligament of Cooper), bridging over the notch on the inner margin of the trochlear notch, and stretching from the olecranon process to the coronoid process.

The flexor digitorum sublimis muscle is attached to the ligament.


Posterior Ligament


Posterior Fibres of Lateral Ligament


Fig. 323.—The Right Elbow-Joint (Lateral Aspect).


. , notch on the inner margin of the trochlear notch of the ulna, together \m the bridging ligament, completes a foramen or deficiency in the capsule t irongh which the extra-articular fat on the inner aspect of the joint is con








THE UPPER LIMB


519


tinuous with an intra-articular pad of fat occupying a rough non-articular area crossing the trochlear notch. When a relatively larger amount of the trochlear of the humerus occupies the trochlear notch of the ulna, fat is extruded through this deficiency. On the other hand, when a lesser amount of the trochlea occupies the trochlear notch, fat is drawn into the joint. The former occurs in extension, the latter in flexion, of the joint.

The synovial membrane lines the deep aspect of the capsule, and below is continuous with that of the superior radio-ulnar joint, lining the deep surface of the orbicular ligament and the upper part of the neck of the radius. It also lines the coronoid, radial, and olecranon fossae of the humerus.

Muscular Relations. — Ihe capsule is closely related to the following muscles: anteriorly, brachialis; posteriorly , the triceps and the anconeus;


Fig. 324.—The Right Elbow-Joint (Medial Aspect).


laterally, the extensor carpi radialis brevis and supinator; and medially, the flexor digitorum sublimis.

Nerve-supply. —The radial musculo-cutaneous, median, and ulnar nerves.

Movements. —The chief movements are flexion and extension, extension being limited by the tension of the muscles on the front of the joint, and flexion by the approximation of the muscular prominences on the front of the forearm and of the arm respectively. Slight lateral movements can take place in all degrees of flexion. They are very limited when the joint is extended.

Muscles concerned in the Movements.—Flexion is produced by the biceps, brachialis, brachio-radialis, and, as auxiliaries, the muscles arising from the medial epicondyle of the humerus. Extension is produced by the triceps and anconeus, and, as auxiliaries, the muscles arising from the lateral epicondyle.

Bursae at Elbow-Joint. —The bursae m the neighbourhood of the joint are: a subcutaneous bursa between the skin and the triangular








5 20


A MANUAL OF ANATOMY


surface on the back of the olecranon process; a small bursa between the tendon of the triceps and the posterior ligament of the joint; and one between the tendon of the biceps and the’ anterior smooth portion of the tuberosity of the radius. Small bursae over the medial and lateral epicondyles of the humerus may be present, but they are inconstant.


The Radio-Ulnar Joints.

The joints between the radius and ulna are the superior and inferior radio-ulnar. Intermediately the two bones are connected together by the interosseous membrane.

Superior Radio-ulnar Joint.—The articular surfaces are the circumferential articular surface surrounding the head of the radius and the

radial notch of the ulna. The annular (orbicular) ligament is a strong fibrous band which forms about four-fifths of a circle, and surrounds the circumference of the head of the radius, which it retains in contact with the radial notch. Its extremities are attached to the anterior and posterior margins of the radial notch. The ligament is smaller below than above, and thus maintains the head of the radius in position. It gives attachment to ligaments of the elbow-joint and to the supinator muscle.

The synovial membrane is continuous with that of the elbow-joint, and lines the inner surface of the annular ligament and upper part of the neck of the radius.

A loose fold of the synovial membrane, extending from the inner side of the neck of the radius to the lower lip of the radial notch of the ulna, is thickened by the presence of elastic fibres, and is sometimes termed the quadrate ligament.

Muscular Relations.—Extensor carpi radialis brevis and supinator.

Nerve-supply.—The radial nerve.

Inferior Radio-ulnar Joint.—The articular surfaces concerned are the ulnar notch of the radius, the outer side of the head of the ulna, and the upper surface of the articular disc.

The anterior and posterior radio-ulnar ligaments consist of loose and relatively weak fibres in front of and behind the joint, and are attached to the adjacent portions of the radius and ulna; the posterior ligament is thicker than the anterior. The articular disc is more or less triangular when viewed from above or below. Interposed between the ulna and the triquetral, its base is attached to the ridge on the


Fig. 325. —The Upper End of the Ulna, and the Annular Ligament.





THE UPPER LIMB


52i


radius, intervening between the ulnar notch and the carpal articular surface, its apex to the pit at the lower end of the' ulna on the deep aspect of the root of the styloid process. It is thicker in front and behind than it is centrally, and at its ulnar attachment than it is at its radial. Its anterior and posterior borders are adherent to the anterior and posterior ligaments. It is sometimes perforated, in which case the synovial cavities of the inferior radio-ulnar joint and of the wristjoint are continuous with one another.

The synovial membrane of the joint is very loose, and is known as the membrana sacciformis. It consists of two parts, vertical and horizontal, the two being continuous with each other; the former is associated with the joint between the head of the ulna and the ulnar notch of the radius, the latter with that between the lower end of the ulna and the upper surface of the articular disc.

Nerve-supply.—The anterior and posterior interosseous nerves.

The Intermediate Joint between the Radius and Ulna is an extended syndesmosis. The shafts of the two bones do not come into close approximation, but are connected together by the interosseous membrane and the oblique ligament.

The interosseous membrane is a strong expansion which stretches between the interosseous borders of the shafts of the radius and ulna, and is deficient at the upper end of the interspace between the two bones. The direction of its fibres is obliquely downwards and outwards from the radius to the ulna; some fibres, however, are disposed in the opposite direction. The upper limit of its radial attachment is about 1 inch below the radial tuberosity. The terminal branch of the anterior interosseous artery traverses its lower part. In addition to connecting the shafts of the two bones together, the membrane gives attachment to the deep muscles on the front and back of the forearm.

Relations— Anterior .—The flexor digitorum profundus and flexor pollicis longus, with the anterior interosseous vessels and nerve lying deeply between the two. The pronator quadratus lies in front of its lower part. Posterior .—From above downwards the supinator, abductor pollicis longus, extensor pollicis brevis, extensor pollicis longus, extensor indicis, and, for a short distance below, the posterior interosseous nerve and posterior branch of the anterior interosseous artery. Above .—The posterior interosseous artery as it passes backwards to gain the back of the limb. Below .—The inferior radio-ulnar joint.

The oblique cord is a narrow band which extends obliquely upwards and inwards from the lower and back part of the tuberosity of the radius to the tuberosity of the ulna. Between it and the upper free edge of the interosseous membrane is a triangular interval bounded medially by the shaft of the ulna and occupied by the posterior interosseous artery.

The movements taking place at these joints are those of pronation and supination, the latter being the more forcible. In pronation the lower part of the radius, carrying the hand with it, crosses over the lower part of the ulna to such an extent as to lie on its inner side, the dorsum of the hand being directed


522


A MANUAL OF ANATOMY


upwards. In supination the lower end of the radius and the hand move in the opposite direction, and when the movement is complete the lower part of the radius lies on the outer side of the ulna, the palm of the hand being directed upwards. At the superior radio-ulnar joint the head of the radius rotates axially upon the capitulum of the humerus within the ring provided by the radial notch of the ulna and the annular ligament. At the inferior radio-ulnar joint the radius rotates upon the head of the ulna, the movement being one of circumduction about an oblique axis passing through the centre of the head of the radius above to the styloid process of the ulna below. There is also limited movement of the ulna, the lower end of that bone moving outwards and backwards in pronation, and inwards and forwards in supination.

As the articular disc is attached to the styloid process of the ulna— i.e., to a point on the imaginary axis, about which the rotation of the lower end of the radius takes place—it maintains apposition between the ulnar notch of the radius and the head of the ulna, and is equally tense in all positions of supination and pronation.

Muscles concerned in the Movements— (i) Pronation. —The principal pronating muscles are the pronator teres and pronator quadratus. (2) Supination. —The biceps is the chief supinating muscle, and is assisted by the supinator. The brachio-radialis is also a feeble supinator, but can only come into play when the hand is fully pronated.


The Radio-Carpal or Wrist Joint.

The articular surfaces concerned are the carpal surface of the radius and the articular disc above, and the upper facets of the scaphoid, lunate, and triquetral, with the interosseous ligaments between them below. The carpal surface of the radius together with the articular disc form an oval socket, into which an oval convexity provided by the proximal row of the carpal bones is received. The articular surface extends farther on to the dorsal aspect than on to the palmar aspect of the carpus. The ulna is excluded from the joint by the articular disc. Ihe joint is surrounded by a capsule, in which anterior, posterior, lateral, and medial ligaments may be distinguished.

The anterior ligament (Fig. 326) consists of two parts: An outer broad, thick band of fibres which sweep obliquely downwards and inwards from the anterior aspect of the lower end of the radius, and its styloid process to the lunate, triquetral, and capitate. The inner band is narrower, weaker, and more vertically disposed; it extends downwards from the articular disc of the wrist to the triquetral and capitate.

The posterior radio-carpal ligament (Fig. 328) is broad and thick.

It consists of fibres which sweep obliquely downwards and inwards from the posterior border of the radius to the scaphoid, lunate, and cuneiform bones.

It is to be noted that the general direction of the fibres of both the anterior and posterior radio-carpal ligaments is downwards and inwards. This feature is associated with the fact that adduction of the wrist-joint (inward bending of the hand) is a much more extensive movement than abduction.^

Ihe lateral ligament (Fig. 326) is a strong, flattened band which extends from the tip of the styloid process of the radius to the tubercle of the scaphoid.


THE UPPER LIMB


523


The medial ligament (Fig. 326) is a rounded cord which extends from the tip of the styloid process of the ulna to the triquetral and pisiform bones.

The synovial membrane lines the deep surface of the capsule and the upper surfaces of the interosseous ligaments between the carpal bones. When the articular disc is perforated, as is sometimes the case, it is continuous with the synovial membrane of the inferior radioulnar joint.

Muscular Relations— Anterior .—From within outwards, the flexor carpi ulnaris, flexor digitorum profundus, flexor pollicis longus, and flexor carpi radialis. Posterior .—From within outwards, the extensor carpi ulnaris, extensor digiti minimi, extensor digitorum with the


Radius_ _ _



Tntpmssf^nns Membrane

1-^

i_Ulna


Anterior Radio-Carpal_

Ligament

Lateral Ligament — Ligaments of ist Row —

Lateral Ligaments of ist and 2nd Rows

Ligaments of 2nd Row

Capsule of Carpometacarpal J oint of Thumb


_Anterior Radio-ulnar

Ligament

Medial Ligament

_ Flexor Carpi Ulnaris


Pisiform Bone

Ligaments of ist & 2nd Rows

-Piso-hamate Ligament

-Piso-metacarpal Ligament

_Hook of Hamate


Intermetacarpal Ligaments


2.M.


3.M 4.M

Fig. 326.—The Ligaments of the Radio-carpal, Carpal, Carpo-metacarpal, and Intermetacarpal Joints (Anterior View).


extensor indicis, extensor pollicis longus, extensor carpi radialis brevis, and extensor carpi radialis longus. Lateral .—The abductor pollicis longus and extensor pollicis brevis.

Nerve-supply.—The median, ulnar, and posterior interosseous nerves.

Movements. —The movements taking place in the joint are flexion, extension, adduction, and abduction. Adduction is much more extensive than abduction. When the hand is in line with the forearm, the scaphoid facet on the radius articulates with the scaphoid bone, and the lunate facet of the radius, together with the articular disc, articulate with the lunate bone, the proximal articular surface of the triquetral being in contact with the inner portion of the capsule. When the hand is adducted, the proximal articular surface of the triquetral articulates with the articular disc, the lunate partially articulates with the scaphoid facet of the radius, and the scaphoid bone is in partial contact with the outer portion of the capsule.





524


A MANUAL OF ANATOMY


The Joints of the Hand.

The Intercarpal Joints.—The carpal joints are classified into thos( between the individual bones of the proximal row, those between th( individual bones of the distal row, and the transverse carpal joint, o] the joint between the proximal and distal rows.

Joints of the Proximal Row .—The bones, with the exception of the pisiform, are united together by dorsal, palmar, and interosseous ligaments. The dorsal and palmar ligaments are more or less transversely disposed, and join the corresponding surfaces of the three bones together. The interosseous ligaments (Fig. 327) are placed one or

either side of the lunate, and connect it with the scaphoid and triquetral. They unite the upper or proximal parts of the bones together, and help tc form the carpal articular surface of the radio-carpal joint.

The synovial cavities between the bones are continuous with that of the transverse carpal joint.

Pisiform Joint .—The pisiform bone is united to the front of the triquetral by a capsular ligament which surrounds the joint, and is attached to the circumferential edges of the opposed articular surfaces. Above the capsule is connected with the tendon of insertion of the flexor carpi ulnaris, and below with the piso-hamate and piso-metacarpat ligaments. I lie tormer is attached to the hook of the hamate bone, and the latter to the base of the fifth metacarpal. By means of these ligaments the contraction of the flexor carpi ulnaris is exerted upon the distal row of the carpus and the metacarpus.

The pisiform joint has an independent synovial cavity.

Joints of the Distal Row .—The four bones of the distal row are connected together by dorsal, palmar, and interosseous ligaments, which are disposed similarly to those of the first row.

Ihe three interosseous ligaments present a contrast to those of the proximal row m that they connect the middle parts of the opposed surfaces of the four bones together. As they do not fill up the intervals between the dorsal and. palmai surfaces of the bones completely, the synovial cavities extend across lem, and the transverse carpal joint is thereby put into communication with the carpo-metacarpal joints.


Radius


Ulna


Radio-carpal

Membrane


Membrana

Sacciform is


Fig. 327.— Radio-carpal and Carpal Synovial Cavities.



THE UPPER LIMB


525


Transverse Carpal Joint (Fig. 327).—The articular surface of the proximal row is convexo-concave, that of the distal row concavoconvex, in each case from without inwards. The convexity of the proximal row is formed by part of the scaphoid, and the concavity by part of the scaphoid and by the lunate and triquetral. The concavity of the second row is formed by the trapezium and trapezoid, and the convexity by the head of the capitate and part of the hamate. The two rows are connected by dorsal, palmar, and lateral ligaments. The dorsal and palmar ligaments are somewhat indefinite, but for the most part radiate from the capitate. The lateral ligament of the wrist-joint connects the scaphoid with the trapezium, and the medial the triquetral with the hamate.

The Carpal Synovial Cavity of the transverse carpal joint is continuous above with the two synovial cavities, one on either side of the lunate bone, these being limited proximally by the interosseous ligament. Below it is continuous with the three synovial cavities between the four bones of the distal row, and these, in their turn, are continuous with the synovial cavities of the four inner carpo-metacarpal joints.

Nerve-supply.—The median, ulnar, and posterior interosseous nerves.

Movements. —The gliding movements taking place between the individual bones of each row are extremely limited. The movements at the transverse carpal joint are less restricted, and render the flexion and extension movements of the radio-carpal joint more extensive. The numerous joints bestow considerable strength and elasticity to the wrist, and thereby enable it to minimize the effect of shock or jar which may be transmitted from the hand to the forearm.

Carpo-metacarpal Joints— Inner Four Joints. —The bones concerned are the trapezium, trapezoid, capitate, and hamate proximally, and the bases of the four inner metacarpal bones distally. The ligaments connecting the bones are dorsal, palmar, and interosseous. The second, third, and fourth metacarpal bones receive each two dorsal ligaments from two adjoining carpal bones; the fifth, as a rule, receives one from the hamate only. The palmar ligaments are usually one to each joint. There is one interosseous ligament, which connects the adjacent parts of the capitate and hamate with the inner aspect of the base of the third metacarpal bone.

These joints derive their arterial supply from the radial and ulnar arteries, and their nerve-supply from the deep division of the ulnar nerve and the posterior interosseous nerve.

Movements. —The movements are those of slight flexion and extension. Lateral movements also take place in varying degree, leading to separation and approximation of the distal ends of the metacarpal bones.

Carpo-metacarpal Joint of the Thumb. —-The articular surfaces taking part in the joint between the trapezium and the base of the first metacarpal are reciprocally saddle-shaped. They are connected together by a capsular ligament, which is attached round the margins of the two articular surfaces, and is strongest on the dorsal and outer aspects. This ligament is sufficiently loose to allow of considerable movement.


526


A MANUAL OF ANATOMY


The synovial cavity is independent of the other carpo-metacarpal joints.

Nerve-supply.—The median nerve.

Movements. —The movements allowed are flexion, extension, abduction, and adduction. At this joint the movements of opposition, whereby the tip of the thumb is brought in such position that it can be easily opposed in succession to the tip of each of the four lingers, take place.

Intermetacarpal Joints (Fig. 327).—The bones concerned are the bases of the four inner metacarpals, the first metacarpal bone not coming into approximation with the second. The ligaments are dorsal, palmar, and interosseous. The dorsal ligaments are composed of stout fibres transversely disposed. The palmar ligaments are


Interosseus Membrane

Ulna


Posterior Radio-ulnar_

Ligament

Medial Ligament —


Ligaments between ist and 2nd Rows


Ligaments of 2nd Row-.-_v


Intermetacarpal Ligament

Radius


Styloid Process of Radius

Posterior Ligament

Lateral Ligament

Ligaments of ist Row

Lateral Ligament of ist and 2nd Rows

Carpo-metacarpal Ligaments

Capsule of Carpo-metacarpal Joint of Thumb


3.M


hie. 3^8. Ligaments of the Radio-carpal, Carpal, Carpo-metacarpal, and Intermetacarpal Joints (Posterior View).


similarly disposed in front. The interosseous ligaments are strong bundles which pass between the opposed surfaces of the bases; their attachments are distal to the articular facets.

Nerve-supply.— The deep division of the ulnar nerve.

The synovial cavities are continuous with those of the carpo-metacarpal joints.

The heads of. the four inner metacarpal bones are connected by deep transverse ligaments of palm. They extend transversely across the palmar aspects of the heads, and their fibres are attached to the fibrous plates on the palmar surfaces of the metacarpo-phalangeal jom s. hey receive the deep lateral slips of the digital processes of the central pait of the palmar aponeurosis, and in the intervals between








THE UPPER LIMB


52 7


the bones the digital arteries and nerves pass in front of them and the interosseous muscles behind them.

Metacarpo-phalangeal Joints. —In each joint the rounded head of a metacarpal bone articulates with the cup-shaped depression on the adjoining surface of a proximal phalanx.

Inner Four Metacarpo-phalangeal Joints. —Each joint is provided with four ligaments—capsular, palmar, and two collateral. The collateral ligaments are strong bands attached proximally to the dorsal tubercle and palmar depression on either side of the head of a metacarpal bone, and distally to the side of the base of a proximal phalanx; it is also attached to the lateral margin of the palmar ligament. Each collateral ligament is connected with a deep lateral slip from a digital process of the central part of the palmar aponeurosis. The palmar ligament, the thickened palmar part of the capsular ligament, is in the form of a fibro-cartilaginous plate. It is closely attached on either side to the collateral ligaments, distally to the palmar aspect of the base of the proximal phalanx, and proximally it is connected with the deep transverse ligaments of palm, and also has a slight attachment to the palmar aspect of the head of a metacarpal bone, close to the edge of the articular cartilage. On its deep aspect is a fibro-cartilaginous lip which projects backwards and occupies to some extent an interval between the articular surfaces; it increases the extent of the phalangeal socket for the reception of the head of a metacarpal bone. Its anterior or superficial surface is grooved, and forms the floor of the tunnel for the passage of the flexor tendons. The posterior part of the capsular ligaments is exceedingly thin, and is with difficulty separable from the extensor tendon, which is closely applied to the dorsal aspect of the joint, and is adherent to the ligament.

Nerve-supply. —The deep division of the ulnar nerve.

Movements. —The movements are chiefly flexion and extension. Lateral movements are also possible, these lateral movements occurring when the fingers close and separate during flexion and extension respectively.

Metacarpo-phalangeal Joint of the Thumb. —The collateral ligaments of this joint are similar to those of the other joints, but there is no palmar fibro-cartilaginous plate. The two common tendons of the short muscles of the thumb (Fig. 309) attached to the base of the proximal phalanx blend with the capsular ligament on the front of the joint, and two sesamoid bones, comparable in size and form to split peas, are present where the blending occurs. The palmar surface of each sesamoid bone is convex; the deep surface is almost flat, covered by cartilage, and plays upon a groove on the palmar surface of the head of the first metacarpal bone. The two bones are united by fibres which pass between their adjacent surfaces and are related superficially to the tendon of the flexor pollicis longus. Distally they are connected by fibres with the palmar aspect of the base of the proximal phalanx. At either side they are connected with the collateral ligaments, and proximally the connection with the head of the first metacarpal close to the edge of the articular cartilage is a weak one. The posterior part of the capsular ligament is very thin, and closely associated with the extensor tendons.

Nerve-supply.—The median nerve.

Movements. —Flexion, extension, and slight lateral movements.

Interphalangeal Joints.—These joints are similar to the metacarpophalangeal joints, each joint being provided with a capsular ligament and two collateral ligaments—a palmar ligament with a fibro-cartilaginous lip projecting backwards into the joint cavity, and a very thin dorsal ligament adherent to the extensor tendon. The nerve-supply is derived from the digital nerves.

The movements are limited to flexion and extension, the former being very free but the latter limited.