Page:The New International Encyclopædia 1st ed. v. 14.djvu/423

* NERVOUS SYSTEM AND BRAIN. 373 NERVOUS SYSTEM AND BRAIN. smalk'i" lliau llie aiilLiiur and aru distributed to till' muscles and skin uf the back. The antc'iiiir divisions of the spinal nerves supply llie anterior parts of the body and the extreiuilies. Kach anterior branch is connected by some slender filaments with the sympathetic. In the dorsal refjion tlie anterior divisions are separate and distributed quite evenly, but in the cervical, hunliar, and sacral regions they unite to form intricate plexuses. T]iic ('i;!tvKAL I'LEXis. This is formed by the anterior divisions of the first four cervical nerves. The branches of distribution of this plexus may be divided into a superficial set and a deep set, the former supplying the integument and the more superficial muscles of (he side and front of the neck and upper part of the throat; the latter supplying the more dee])ly seated muscles of the neck and sending one very important branch, the phrenic, to the diaphragm. C.WITH PHRSU/C ens. TOLOnbus COUt 6 SCALENI Rhomboid Sub-clayioTi Strpra -scGpuJar Ext.ani.ihoraeic Upper sub- scapular 'Ou/ercord. Ctrcu/nfUx ■Sub-scapular -Posteriorcord PLAN OF THE BRACHIAL PLKXU8. The brachial plexus is formed by the anterior divisions of the last four cervical and the first dorsal nerves. These five nerves unite to form three main cords known respectively as the outer, the inner, and the posterior cords of the brachial plexus. Before uniting to form these cords, four main branches or sets of branches are given oft". These are ( 1 ) a communicating branch to the phrenic; (2) muscular branches to the longus colli, scaleni, rhomboidei, and subelavius; (3) posterior thoracic nerve, to the serratus mag- nus ; (4) the supra-scapular, sending branches to supply the supra- and infraspinatus. From the three main cords of the plexus branches are given 00" to the chest, shoulders, and arms. Those to the clicst are the external and internal ante- rior tlioracic, which supply the pectoralis major and pectoris miniu' r.uiscles. The branches to the shoulder are the subscapular and the circum- flex, the former supplying the subscapularis, the lalissimus dorsi. and the teres major; the latter supplj'ing the deltoid and the teres minor. The circumflex nerve also supplies part of the in- tegument of the shoulder and sends filaments to the musculocutaneous nerve. This nerve in the arm supplies the biceps, eoraco-brachialis. and part of the brachialis anticus muscles. In the forearm it becomes cutaneous, supplying the in- tegument on the radial side. The internal cu- taneous nerve is a small nerve to the integument of the front of the arm and forearm. The lesser internal cutaneous or nerve of Wrisberg, the smallest branch of the plexus, is a branch to the integument on the inner side of the arm. The musculo-spiral supplies the triceps, anconeus, supinator longus, ^scormeds wUli 12^^ Dorsal •ui/ta l 2"-''L rural CLAN OF LUMBAR PLEXUS. extensor carpi radialis longior, and part of the brachialis anti- cus. It sends a cutaneous branch to the skin of the outer part of the forearm. It then divides into radial and i)os- t e r i o r interos- seous branches, the former pass- ing to the skin of the radial side of the hand, includ- ing thumb, index, middle and railial side of ring fin- gers ; the latter supplying the carpal articu- lations and muscles of the back of the fore- arm. The ulnar nerve supplies the flexor carpi ulnaris and inner part of the flexor pro- fundus digitorum. In the hand it supplies the adductor and part of the short flexor of the thumb, the interossei, the two inner lumbricales, and the muscles of the ball of the little finger. It supplies a cutaneous branch to the back of the little and ulnar side of the ring fingers, and to the front of the same fingers. It also supplies articular branches to the elbow and w'rist joints. The median nerve supplies all the fle.xors and pronators of the forearm except those supplied by the ulnar. In the hand it supplies the two outer lumbrical muscles, part of the short flexor of the thumb, the opponens and the abductor. It also innervates the skin of the palm and of the palmar surfaces of the fingers not supplied by the ulnar. The linnbar plexus lies at the back of the abdominal cavity behind the peritoneum. It is formed l)y the anterior divisions of the four up- per lumbar nerves. Comnuinicating branches connect the plexus with the luml>ar ganglia of the sympathetic. Some muscular branches pass directly from the plexus to the quadratus lumbo- rum and psoas muscles. Cutaneous branches are the (I) iliohypogastric, which sends an iliac branch to the skin of the buttock and a hypoglos- sal branch to the skin of the lower abdomen; (2) the ilioinguinal, to the skin of the groin; (3) the external cutaneous, to the skin of the outer side of the thigh. Mixed branches of the plexus are ( 1 ) the genito-crural. to the skin of the groin and to the cremaster mu.scle ; (2) the an- terior crural, a large and important branch which supplies the sartorius, the peetineus, the psoas iliacvis, and the extensors of the knee joint, be- sides giving off three cutaneous branches, the internal cutaneous to the skin of the inner aspect of the thigh, a middle cutaneous to the skin of the front of the thigh, and the long saphe- nous to the skin of the inner side of the knee, leg, and foot; (3) the obturator, which