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To understand the effect of lesions of the spinal medulla, it is necessary to be familiar with the sensory and motor distributions of the various spinal segments (see Figs. 609, p. 693, and 607, p. 688). Transverse lesions of the spinal medulla above the fifth cervical spine (that is, above the fibro-cartilage between the fourth and fifth cervical vertebræ) are quickly fatal, owing to paralysis of respiration, as the phrenic nerve arises mainly from the fourth segment. In transverse lesions of the cervical enlargement the cutaneous insensibility does not extend higher than a transverse line at the level of the second intercostal space.

The diagnosis of the particular segment involved is arrived at by testing the motor and sensory functions of each segment. The sensory areas corresponding to the lower four cervical and the first two thoracic segments occupy the upper extremities, and are placed in numerical order from the lateral to the medial side of the limb. The sensory area corresponding to the second, third, and fourth cervical segments occupy the occipital region of the scalp, the back of the auricle, and the masseteric region, the whole of the neck, and the shoulders and upper part of the chest down to a horizontal line at the level of the anterior end of the third intercostal space. In a total transverse lesion of the spinal medulla in the thoracic region, the superior limit of the anesthesia is horizontal, and reaches to the level of the terminations of the anterior rami of the spinal nerves which arise from the spinal segment opposite the vertebral injury. Hence the superior limit of the anæsthesia is at a much inferior level than that of the injured vertebra. For example, a fracture-dislocation at the level of the eighth thoracic vertebra involves the origin of the tenth thoracic nerve which ends at the level of the umbilicus. The sensory zone corresponding to the fifth thoracic segment is at the level of the nipples, that of the seventh thoracic segment is at the level of the xiphoid process, that of the tenth at the level of the umbilicus, while that of the twelfth reaches down, anteriorly, to the superior border of the symphysis. The sensory areas corresponding to the lumbar and sacral segments are seen in Figs. 627, p. 725, and 629, p. 733.

THE UPPER EXTREMITY.

THE SHOULDER.

The bony landmarks of the shoulder must be systematically examined in all injuries about that region. The medial extremity of the clavicle is prominent; its articulation with the sternum forms essentially a weak joint, which is liable to be dislocated, especially from blows upon the lateral part of the shoulder which drive the medial end of the clavicle forwards against the weak anterior sterno-clavicular ligament. The body of the clavicle, subcutaneous throughout, is weakest at the junction of its two curves; it is in that region that the bone is so frequently fractured as the result of force transmitted through it to the trunk. The displacement of the lateral fragment varies according to whether the break takes place medial or lateral to the coraco-clavicular ligament; in the former case the weight of the upper extremity, acting through the coraco-clavicular ligament, pulls the lateral fragment downwards; when the fracture is lateral to the ligament, the lateral end of the clavicle rotates forwards, but there is no downward displacement. The lateral end of the clavicle is on a plane posterior to its medial end, so that the shoulder is braced backwards away from the thorax; hence in fractures of the clavicle, both medial and lateral to the coraco-clavicular ligament, the point of the shoulder rotates forwards and medially. The acromio-clavicular articulation is somewhat difficult to feel; the groove which corresponds to it runs in the sagittal direction, and lies 14 in. medial to the lateral border of the acromion, and immediately lateral to a slight prominence upon the lateral extremity of the clavicle. When the acromioclavicular joint is dislocated the clavicle almost invariably overrides the acromion, and the summit of the shoulder presents a somewhat conical or "sugar-loaf" appearance.

The tip of the acromion looks directly forwards, and lies a finger's breadth lateral to and a little in front of the lateral extremity of the clavicle. The lateral border of the acromion can readily be followed to its junction with the spine of the scapula, and the latter to its root, which is situated on a level with the third thoracic spine. The medial border of the acromion and the posterior border of the lateral end of the clavicle meet at an angle into which the point of the finger can

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d. The medial angle of the scapula, covered by the trapezius and the
atus muscles, is too deeply placed to be palpated distinctly. The inferior
1 the vertebral border, from the root of the spine downwards, form visible
ces which are readily felt; the inferior angle overlies the seventh inter-
ace on a level with the seventh thoracic spine, while the vertebral border
tle medial to the angles of the ribs.
icit crepitus in a transverse fracture of the scapula below the spine, the surgeon
ehind the patient and grasps the upper fragment by placing the forefinger upon
coid and the thumb upon the spine, while, with the other hand, he grasps the
angle ; the two fragments are then moved the one upon the other.
e tip of the coracoid process may be felt by pressing the finger firmly upon the
r border of the deltoid at a point one inch below the junction of the middle
teral thirds of the clavicle. Medial to the coracoid is a triangular depres-
hich corresponds to the superior end of the interval between the clavicular
of the pectoralis major and deltoid muscles. Behind this triangular depres-
are the termination of the cephalic vein, a lymph gland, the first part of
xillary vessels, and the cords of the brachial plexus. By firm pressure in this
tion the pulsation of the axillary artery can be felt, and by further pressure
irculation in the vessel can be arrested by compressing the artery against the
ad rib. The first part of the axillary artery may be cut down upon either by
insverse incision through the clavicular origin of the pectoralis major, or by a
itudinal incision in the interval between that muscular slip and the deltoid.

companion vein lies in front of, as well as to the thoracic side of, the artery,
s adding to the difficulty of exposing the vessel. In fractures of the middle
rd of the clavicle the subclavian vessels are protected by the soft pad formed by
subclavius muscle.

The proximal extremity of the humerus, covered by the deltoid, gives rotundity the shoulder. The greater tubercle projects beyond the acromion, and constitutes e most lateral bony landmark of the shoulder. When the head of the bone is slocated, the lateral border of the acromion then becomes the most lateral bony andmark, and the shoulder presents a square contour. The lesser tubercle, small ut conical, can be felt through the deltoid. Pointing directly forwards, it lies one nch lateral to and a little below the level of the tip of the coracoid process. In xamining the proximal extremity of the humerus for fracture, the tubercles should be grasped between the finger and thumb of one hand, while the flexed elbow is rotated with the other hand. The head of the humerus has the same direction as the medial epicondyle ; its distal part can be palpated through the axilla, the arm being meanwhile abducted, to bring the head in contact with the inferior surface of the capsule. It is through this, the weakest part of the capsule, that the head is driven in the common varieties of dislocation of the shoulder, viz., those due to forcible abduction. The proximal epiphysis of the humerus includes the head and the greater part of the tubercles. The capsule is attached mainly to the epiphysis; hence, in children, we find that separation of the proximal epiphysis takes the place of dislocation. Disease in the proximal end of the diaphysis does not necessarily involve the cavity of the joint. The intertubercular sulcus of the humerus, which lies immediately lateral to the lesser tubercle, may be mapped out upon the surface by drawing a line, two inches in length, distally along the axis of the humerus from the tip of the acromion. When there is effusion into the joint, the arm becomes slightly abducted, and there is fulness in front, along the line of the long tendon of the biceps. With the elbow at the side the lower part of the capsule of the shoulder-joint is loose and folded upon itself to form a dependent pocket; if, after an injury, the arm is retained too long in this position, the patient may be unable to abduct the arm, in consequence of the formation of adhesions in and around the pouch. To evacuate pus from the shoulder - joint, the integuments, deltoid, and capsule should be cut into by an incision passing vertically and distally from the tip of the acromion.

THE AXILLA.

The anterior fold of the axilla, formed by the inferior border of the pectoralis major, extends from the fifth rib to the middle of the anterior border of the deltoid. With the arm abducted, the interval between the sternal and clavicular fibres of the pectoralis major is indicated by a slight groove extending distally and laterally from the medial end of the clavicle. The sternal fibres, along with the pectoralis minor, are removed in a complete operation for malignant disease of the breast, the pectoral branches of the thoraco-acromial artery being secured as they cross the interval between the sternal and clavicular portions of the greater pectoral. The posterior fold of the axilla, formed by the latissimus dorsi and the teres major muscles, is on a lower level than the anterior fold, and leaves the chest a little in front of the inferior angle of the scapula. Between the two folds, and running in the long axis of the limb, from the axilla to the middle of the arm, is the prominence of the coraco-brachialis muscle. The pulsations of the third part of the axillary artery may be felt in the furrow, immediately behind this prominence, at the junction of the anterior and middle thirds of the lateral wall of the axilla.

Female Mamma.—The breast tissue proper is arranged to form a central portion, the corpus mamma, and a peripheral portion, made up of branching processes which radiate into the paramammary fat and become continuous ultimately with the connective tissue septa of the subcutaneous fatty tissue. The mamma, therefore, has no distinct capsule. In the young adult nullipara, the corpus mamma is compact and well defined, and contains but little intramammary fat, while the peripheral processes are relatively small. In multipara, the corpus mammæ contains more fat, and the peripheral processes extend more widely into the paramammary fat.

The arrangement and extent of the parenchyma can be well seen by treating the breast with a 5 per cent. solution of nitric acid. If slices of the fresh organ are placed in this solution for a few minutes and then washed under running water, the albumen of the epithelial cells of the parenchyma is coagulated, while the connective tissue is rendered translucent and somewhat gelatinous. The ultimate lobules of the parenchyma now appear as little (1 to 2 mm.), dull, opaque, white, sago-like bodies, arranged in grape-like clusters around the finer branches of the ducts.

The parenchyma is prolonged into the peripheral processes, into the suspensory ligaments of Cooper, and into the loose retromammary cellular tissue and pectoral fascia. The breast tissue, therefore, has a much wider distribution than was formerly supposed. Vertically, it extends from the second rib to the sixth costal cartilage at the angle where it begins to ascend towards the sternum; horizontally, from a little medial to the lateral border of the sternum, opposite the fourth rib, to the fifth rib in the mid-axillary line. The medial hemisphere of the mamma rests almost entirely on the pectoralis major; at its lowest part it slightly overlies the upper part of the aponeurosis covering the rectus abdominis muscle. The superior quadrant of the lateral hemisphere rests upon the greater pectoral, on the edge of the lesser pectoral, and to a slight extent on the serratus anterior, upon which it extends upwards into the axilla as high as the third rib, where it comes into relation with the thoracic group of axillary lymph glands. The remainder of the lateral hemisphere rests almost entirely upon the serratus anterior, except the lowest part, which overlaps the digitations of the external oblique arising from the fifth and sixth ribs. It follows, therefore, that fully one-third of the whole mamma lies inferior and lateral to the acillary border of the pectoralis major muscle. The surgeon must cut beyond the above limits if he wishes to remove the whole of the mammary tissue.

The axillary fascia resists the spontaneous rupture of an axillary abscess, which, therefore, tends to spread upwards beneath the pectorals, and towards the root of the neck. To

open the abscess the incision should be made upon the medial wall, behind, and parallel to, the lateral thoracic artery, which runs under cover of the anterior fold.

The axillary lymph glands vary greatly in size and number; many are no larger than a pin's head. In the female some of them undergo au adipose functional involution, whereby they come to resemble fat lobules. In health, one or two glands can usually be felt by thrusting the fingers upwards and medially beneath the anterior fold, the arm

y slightly abducted, so as not to stretch the axillary fascia.

The central group ibedded in the fat immediately beneath the axillary fascia, become inflamed in wounds of the upper extremity. The same group, along with the pectoral group to the medial wall of the axilla, at the inferior border of the pectoralis minor), are the first to become diseased in malignant affections of the breast. When the s more advanced the posterior (subscapular) and the apical (subclavicular) groups rally affected as well, and Rotter has shown that in a considerable porportion of seased glands are to be found in the retro-pectoral fascia, i.e. between the pectoralis nd minor and, above the latter muscle, on the first intercostal space in relation to preme thoracic artery. In operating for malignant disease of the breast, the n removes, in addition to the whole breast and the greater part of the skin over it, ectoral muscles (with the exception of the clavicular fibres of the pectoralis major), Brachial artery

Clavicle
Biceps tendon

Anterior axillary fold
Brachio-radialis

Coraco-brachialis Deltoid
Biceps

[graphic]

Flexor muscles

Lacertus fibrosus
Medial epicondyle

Brachialis

Ulnar nerve
Medial intermuscular septum

Median nerve
Medial head of triceps

Long head of triceps
Lower border of teres major

Posterior axillary fold
Fig. 1112.- AXILLA, MEDIAL ASPECT OF ARM AND ELBOW.

all the axillary lymph glands, and, as far as possible, all the fat and fascia, including the sheath of the axillary vein. It must be remembered that the distal part of the axillary vein lies immediately underneath the deep fascia of the lateral wall of the axilla ; in cleaning the medial wall the long thoracic uerve must not be injured ; and in removing the posterior group of lymph glands the thoraco - dorsal nerve, which accompanies the subscapular vessels, must be avoided, as it is doubly important to retain the action of the latissimus dorsi after removing the pectorals. The writer has so frequently met with disease in these retro-pectoral glands, that he is convinced of the necessity of removing the pectoral muscles.

THE ARM.

The anterior and posterior borders of the deltoid may be traced from the shoulder girdle to the insertion of that muscle. The surface relations of the anterior border have already been referred to; the posterior border forms a well-marked and important landmark as it crosses the angle between the axillary margin of the scapula and the proximal part of the body of the humerus. By making an incision along this part of the posterior border of the deltoid, and retracting the edge of the muscle upwards and laterally, we expose the surgical neck of the humerus, and the quadrilateral opening in the posterior wall of the axilla, transmitting the posterior circumflex artery of the humerus and the axillary nerve; a little more distaÎly is the radial nerve. The coraco-brachialis, the guide to the proximal half of the brachial artery, forms a prominence occupying the proximal half of the medial bicipital furrow. Traced distally the medial bicipital furrow widens out into an elongated triangle. This triangle, which may be termed the medial supracondylar triangle, becomes continuous, distally, with the medial part of the triangle in front of the bend of the elbow, and is limited posteriorly by the medial intermuscular septum, which may be felt as a cord-like band extending proximally from the medial epicondyle ; the floor of the space is formed by the medial part of the brachialis. Within the triangle are the following important structures, enumerated from the lateral to the medial side, viz.: the brachial artery, the median nerve, the distal part of the basilic

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vein, the medial cutaneous nerve of the forearm, and the superficial cubital lymph glands, two or three in number. Extending proximally from the lateral epicondyle to the insertion of the deltoid is the lateral intermuscular septum, which is pierced at the junction of its proximal and middle thirds by the radial nerve. Between the lateral intermuscular septum and the lateral edge of the biceps is the ill-defined lateral bicipital furrow, the floor of which is formed by a strip of the brachialis, and, nearer the elbow, by the brachio-radialis and extensor carpi radialis longus.

The posterior compartment of the arm is occupied by the triceps, the long head of which can be traced proximally to the axillary margin of the scapula, in front of the posterior border of the deltoid and behind the posterior fold of the axilla. The lateral head of the triceps, after emerging from under cover of the distal part of the posterior border of the deltoid, is continued obliquely along the lateral aspect of the arm as a well-marked muscular elevation. Proximal to the olecranon is the strap-like tendon of insertion of the triceps, which, when the elbow is fully flexed, forms an admirable posterior splint in supracondylar fractures of the humerus.

The brachial artery, slightly overlapped in the proximal half of the arm by the coraco-brachialis and in the distal half by the biceps, can be felt pulsating throughout the whole length of the anterior part of the medial bicipital furrow. The

Head of radius Extensor carpi radialis brevis
Lateral epicondyle

Deep branch of radial nerve
Extensor carpi radialis longus

Abductor pollicis longus
Radial nerve

Middle thecal tuberele
Lateral intermuscular septum, Biceps

Styloid process of Axillary nerve

third metacarpal

[graphic]

Head of ulna
Dorsal border of ulda

Flexor carpi ulnaris
Triceps tendon

Extensor carpi ulnaris
Lateral head of triceps

Extensor digitorum communis
Posterior border of deltoid Anconaus
Long head of triceps

Tip of olecranon
Teres major
Latissimus dorsi

FIG. 1113.- DORSAL ASPECT OF ARM.

Infraspinatus

course of the vessel may be mapped out upon the surface by drawing a line from the medial border of the coraco-brachialis, at the level of the posterior fold of the axilla, distally to a point (opposite the neck of the radius) } in. distal to the middle of the bend of the elbow. In ligaturing the vessel, the edges of the coraco-brachialis and biceps muscles, together with the median nerve, furnish valuable guides to the artery, the mobility of which is often a source of trouble in performing the operation.

The basilic vein, which is superficial to the deep fascia in the distal third of the arm, is visible in the medial supracondylar triangle and the distal part of the medial bicipital groove. The cephalic vein ascends a little anterior and medial to the lateral edge of the triceps to reach the interval between the deltoid and pectoralis major.

The surface guide for the median nerve is the same as that for the brachial artery. The ulnar nerve is indicated superficially by a line extending from the lateral wall of the axilla, immediately posterior to the prominence of the coracobrachialis, to the back of the medial epicondyle; in the proximal half of the arm the nerve lies close behind the brachial artery under cover of the basilic vein, while in the distal half it lies a little posterior to the medial intermuscular septum, partially imbedded in the fibres of the medial head of the triceps. To map out the course of the radial nerve, first mark the point where it pierces the lateral intermuscular septum, viz., the junction of the proximal and middle thirds of a line extending from the insertion of the deltoid to the lateral epicondyle; from that

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