Describe the posterior tibial nerve.

It is a continuation of the former, runs down the middle of the back of the leg beneath the calf-muscles to divide between the inner malleolus and point of the heel into the internal and external plantar; its branches are :

Muscular, to the tibialis posticus, flexor longus digitorum,. flexor longus hallucis, and the soleus muscles; articular, to the ankle-joint.

Plantar cutaneous, to the skin of the heel and inner side of the sole of the foot.

Fibular branch, to the vessels, periosteum, and medullary canal of the fibula.

Internal plantar, supplying the skin of the sole, tarsal and metatarsal joints, one or two inner lumbricals, abductor hallucis, flexor brevis hallucis, and digitorum, four digital branches to both sides of the first, second, and third toes, and inner half of the fourth.

External plantar, smaller than the preceding, supplying the flexor accessorius, abductor, and flexor brevis minimi digiti, all the interossei, two or three outer lumbricals, adductor obliquus, and transversus hallucis, and the skin of the little toe and the adjoining side of the fourth toe.

Describe the external popliteal nerve.

It descends obliquely along the outer side of the popliteal space close to the tendon of the biceps, giving off

Three articular branches to the knee; a cutaneous branch to the skin of the postero-external surface of the leg, and a branch, the communicans peronei, forming part of the external saphenous nerve it divides into the

Anterior tibial, about one inch below the head of the fibula, giving muscular branches to the tibialis anticus, extensor longus digitorum, peroneus tertius, extensor longus hallucis, and extensor brevis digitorum; articular to the tarsal and metatarsal joints, and cutaneous to the skin of the adjacent sides of the great and second toes.

Musculo-cutaneous, giving off muscular branches to the peroneus longus and brevis, and cutaneous to the skin of the lower part of the leg, and dorsum of the foot and toes, except the outer side of the little and adjoining sides of the great and second toes.

Describe the sacral and coccygeal nerves.

They are six in number, their long roots forming the cauda equina in the spinal canal; each divides into an anterior and a posterior division, the latter escaping by the posterior sacral foramina, except the fifth, which emerges between the sacrum and coccyx, and supplies the multifidus spinæ muscle and the skin of the posterior gluteal region; a branch goes from the third and fourth nerves to the bladder; the two lower nerves join with the coccygeal, forming loops, which supply the skin over the coccygeal region and the coccygeus, levator ani, and sphincter ani muscles.

The Sympathetic System.

What is the sympathetic nerve or system?

It consists of (1) a series of ganglia with intervening longitudinal bands, forming two cords, one on each side of the spinal column connected above according to some by the ganglion of Ribes, and below by the ganglion impar or coccygeal ganglion, in front of the coccyx; (2) three prevertebral plexuses, one each for the thorax, abdomen, and pelvis; (3) small ganglia; (4) nerve-fibers of communication with the cerebro-spinal nerves, of distribution supplying the viscera and vessels. Describe the cervical ganglia.

There are three on either side, viz. the

Superior cervical ganglion. It is placed opposite the second and third cervical vertebræ behind the carotid sheath, and gives off a

Superior branch to the internal carotid artery, forming by its division the cavernous plexus and carotid plexus (with their subdivisions);

Descending branch, connecting the superior with the middle ganglion;

External branches to the cranial and spinal nerves, and anterior branches forming plexuses on the external carotid and its branches;

Pharyngeal, forming with branches from the spinal accessory, pneumogastric, glosso-pharyngeal, and external laryngeal nerves, the pharyngeal plexus; laryngeal, uniting with the superior laryngeal nerve and its branches;

Superior cardiac, connected with other branches of the sym

pathetic, and with some of the pneumogastric, passes to the back of the aorta, the right joining the deep, and the left (usually) the superficial cardiac plexus.

Middle cervical ganglion is placed opposite the sixth cervical vertebra; and by its

Superior and inferior branches it communicates respectively with the superior and the inferior cervical ganglia; the external filaments join the fifth and sixth cervical nerves, the internal are the thyroid to the inferior thyroid artery and thyroid gland, and the middle or great cardiac nerve, communicating with other sympathetic branches and the recurrent laryngeal, to terminate in the deep cardiac plexus.

Inferior cervical ganglion is placed between the base of the transverse process of the seventh cervical vertebra and neck of the first rib on the inner side of the superior intercostal artery; its superior and inferior branches connect it respectively with the middle cervical and the first thoracic ganglion; the external branches join the spinal nerves, others form a plexus on the vertebral artery; its chief branch is the

Inferior cardiac nerve, communicating with the recurrent laryngeal and middle cardiac nerves, terminating in the deep cardiac plexus.

What is the carotid plexus ?

It is a plexus situated on the outer side of the internal carotid artery communicating with the Gasserian and spheno-palatine ganglia, the sixth nerve, and the tympanic branch of the glosso-pharyngeal; it supplies the carotid artery and dura mater. What is the cavernous plexus ?

It is one situated below and internal to that part of the internal carotid artery running alongside of the sella turcica, in the cavernous sinus; it communicates with the third, fourth, fifth, and sixth nerves, and ophthalmic ganglion, and supplying the carotid, it, with the carotid plexus, forms plexuses embracing the cerebral and ophthalmic arteries.

What are the other ganglia of the sympathetic system?

Usually eleven thoracic, four lumbar, four or five sacral, ganglion impar, and numerous ganglia connected with the various viscera, whence plexuses are formed named from their locality or the organ involved.

What are the branches of the thoracic portion?

Communicating, with one another and the thoracic spinal nerves, filaments to the aorta and its divisions and to the posterior pulmonary plexus, and

The great splanchnic nerve, formed by the internal branches from the thoracic ganglia between the fifth or sixth and ninth or tenth inclusive; it perforates the crus of the diaphragm to terminate in the semilunar ganglion, sending branches to the renal plexus and suprarenal capsule.

The small splanchnic, springing from the ninth and tenth, or from the tenth and eleventh ganglia and cord communicating with the great splanchnic, pierces the diaphragm with the preceding, to join the celiac plexus.

Smallest, or renal splanchnic, arises from the last ganglion, occasionally communicates with the preceding, pierces the diaphragm, and terminates in the renal and lower part of the celiac plexus.

Describe the solar plexus.

It supplies all the abdominal viscera, consisting of a network of nerves and ganglia lying in front of the aorta and crura of the diaphragm, surrounding the celiac axis and root of the superior mesenteric artery, extending below to the pancreas, and laterally to the suprarenal capsules. The great splanchnic and part of the small splanchnic nerves of both sides and the termination of the right pneumogastric form this plexus, in conjunction with the two semilunar ganglia, these latter being large, irregular gangliform masses, composed of smaller ganglia separated by interspaces, placed by the side of the celiac axis and superior mesenteric artery, close to the suprarenal capsules, that on the right lying beneath the vena cava. From this are derived the following plexuses accompanying the same named arteries to the various organs:

Phrenic, or diaphragmatic,
Gastric,

Celiac Hepatic,

Splenic,

Aortic,

Suprarenal,
Renal,

Superior mesenteric,
Spermatic,

Inferior mesenteric.

Name some of the more important plexuses.

Tympanic (see page 370).

Great, or deep cardiac is placed in front of the bifurcation

of the trachea, and above that of the pulmonary artery, behind the aortic arch, and is formed by all the sympathetic cardiac nerves (except the left superior) and cardiac branches of the recurrent laryngeal and pneumogastric (except the left superior cardiac and the left inferior cardiac of the pneumogastric).

Superficial cardiac lies beneath the aortic arch in front of the right pulmonary artery, and is formed by the left superior cardiac of the sympathetic, left inferior cardiac of the pneumogastric, and branches from the deep cardiac plexus.

Coronary, the posterior, chiefly from the deep, the anterior from the superficial cardiac plexus.

Aortic, on the sides and front of the aorta between the origins of the superior and inferior mesenteric arteries.

Hypogastric, lying in front of the sacrum, between the common iliac arteries, supplies the pelvic viscera, and is formed by filaments from the aortic plexus, and from the lumbar and first two sacral ganglia, contains no ganglia, and divides into two lateral portions, forming the inferior hypogastric or pelvic plexuses.

Pelvic plexuses, two in number, lie upon each side of the rectum and bladder (rectum, vagina, and bladder in females), and each is formed by a continuation of the hypogastric plexus and branches from the second, third, and fourth sacral nerves, and a few filaments from the sacral ganglia; the branches accompany those of the internal iliac artery, and are distributed to all the pelvic viscera; their branches are:

Any of the internal organs with their appendages, contained within the four cavities, cranial, thoracic, abdominal, or pelvic. Of what does the digestive apparatus consist?

Of the alimentary canal, a musculo-membranous tube, lined