tinal, vertebral, and right bronchial veins, also at times it is connected with right superior intercostal vein.

The left lower azygos11 (vena azygos minor) commences by a branch from left lumbar or renal vein, enters thorax through left crus of diaphragm, passes across from the left side of vertebral column at sixth or seventh dorsal vertebra to enter the right azygos vein, receiving veins from four or five lower intercostal spaces; also mediastinal and œsophageal branches.

The left upper azygos12 is formed by veins, usually two to three, from the intercostal spaces between left superior intercostal and highest branch of left lower azygos, and empties into right azygos or left lower azygos; it is sometimes absent, its place being taken by left superior intercostal.

Name the other principal veins of base of the neck and of the thorax.

Internal mammary,

Inferior thyroid,

Intercostals,

Briefly describe the spinal veins.

Mediastinal,

Pericardiac,

Bronchial.

They are the dorsi-spinal on the exterior of the spinal column, forming plexuses around vertebral spines, laminæ, and processes, emptying into intercostal, lumbar, and sacral veins respectively.

The meningo-rachidian, lying between vertebræ and theca spinalis forming plexuses, one running along the posterior surfaces of vertebral bodies forming the anterior longitudinal veins receiving the venæ basis vertebrarum, the other on the inner surface of the laminæ, the posterior longitudinal veins, both extending the whole length of the spinal canal; the posterior emptying into dorsi-spinal, the anterior into vertebral, intercostal, and sacral veins, respectively. The venæ basis vertebrarum, in vertebral bodies, empty into anterior longitudinal.

The medulli-spinal, those of the cord itself, forming a minute. plexus over cord between the pia mater and arachnoid, near base of skull converging to form two or three trunks terminating in the inferior cerebellar veins or petrosal sinuses.

Describe the chief veins of the lower extremity.

They are deep and superficial, the former commence as venæ comites of digitals, which form the interossei, these the anterior and posterior tibial and peroneal accompanying same named arteries, which uniting, form the popliteal, in the thigh to be called the femoral, being joined by profunda femoris and internal saphenous veins, which again changes its name to external iliac above Poupart's ligament; into external iliac en:pty the epigastric and circumflex iliac veins.

The superficial veins are the

Internal or long saphenous, commencing on inner side of dorsum of foot, running up on inside of leg and thigh to enter femoral vein after passing through the saphenous opening of fascia lata; its branches are

Cutaneous,

Superficial epigastric,

Superficial circumflex iliac,
Communicating,

Pudic.

External or short saphenous, commences at outer side of dorsum of foot, passes behind the external malleolus, up the middle of leg posteriorly to empty into popliteal vein between heads of gastrocnemius.

Describe the internal iliac vein.

It is formed by the venæ comites of all branches of external iliac artery except the umbilical, and unites opposite sacro-iliac articulation with external iliac vein to form the common iliac vein; it receives the following veins,

Gluteal, Internal pudic,
Obturator,

Sciatic,

Hemorrhoidal, Uterine and vaginal,
Vesico-prostatic Plexuses, in female,
Plexuses, in male,
Dorsal vein of penis.

Describe the common iliac veins.

Formed by the junction of the external and internal iliac veins, and receiving the ilio-lumbar, occasionally the lateral sacral, and the left iliac the middle sacral vein, they unite at an angle upon the intervertebral substance between the fourth and fifth lumbar vertebræ to form the inferior vena cava.

Describe the inferior vena cava1.

It runs upward from junction of the two common iliacs, along the right side of the aorta, pierces the central tendon of diaphraghm, and terminates at back of right auricle, being partially covered by serous layer of the pericardium; it returns the blood from all parts below the diaphragm, and receives the following branches,

Describe the portal system of veins.

Formed by the union behind the head of the pancreas of the superior and inferior mesenteric, splenic, and gastric veins, collecting the blood from the viscera of digestion, the resulting portal vein divides in the transverse fissure of the liver into a branch each for the right and left lobe, which ramify to form a venous plexus in the liver tissue; the hepatic artery sends branches within the liver to the portal vein, and external to the organ the vein receives the smaller gastric and the cystic vein; the portal blood is returned to the inferior vena cava by the hepatic veins.

What veins return the blood from the substance of the

heart?

Great cardiac vein,

Middle cardiac vein,

Posterior cardiac veins,

What is the coronary sinus?

Anterior cardiac veins,

Right or small cardiac vein,
Vence Thebesii.

A dilatation of about one inch of the great cardiac vein in posterior part of left auriculo-ventricular groove, covered by the muscular tissue of the left auricle and receiving the posterior cardiac veins, and an oblique vein from back of left auricle; its orifice is guarded by the coronary valve.

Describe the pulmonary veins.

Commencing in the lung capillaries they form a main vein for each lobule, which unite into two trunks for each lung, opening separately into the left auricle; at times there are three veins on the right side, or the two left terminate by a common opening.

The Lymphatics.

What are lymphatics?

Delicate vessels with transparent walls formed of same three coats as arteries and found in all parts of the body probably, except the nails, cuticle, hair, and cartilage; they have numerous valves producing their characteristic beaded appearance; they are supplied with nutrient arteries but not with nerves.

What are the lacteals?

The lymphatics of the small intestine, conveying chyle during digestion, lymph at other times.

Describe the lymphatic glands.

They are small solid, round, or ovoid glandular bodies, situated in the course of the absorbent vessels which previous to entering a gland break up iuto several afferent vessels, form a plexus within, and emerge by several efferent vessels which soon unite to form a single trunk; each gland is surrounded by a fibrous capsule which sends partitions inward, forming alveoli in which lies the glandpulp or lymphoid tissue consisting of a rete whose meshes are filled with lymph-cells. The glands are chiefly found in the mesentery, along great vessels, in the mediastinum, axilla, neck, at front of elbow, groin, and popliteal space, being usually named from their locality, as axillary, etc.

Describe the thoracic duct.

This conveys the bulk of the lymph and chyle into the blood, being the common lymph-trunk, except for right upper extremity, right side of head, neck, and thorax, right lung, same side of heart, and convexity of liver. It commences by the triangular receptaculum chyli, on the front of body of second lumbar vertebra, enters the thorax by aortic opening, and opposite the upper border of seventh cervical vertebra it curves downward to empty at the junction of the left internal jugular and subclavian veins.

Describe the right lymphatic duct.

It is about one inch long, receiving lymph from those parts excepted in the account of the thoracic duct, and empties at the junc

Bey.

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tion of the right internal jugular and subclavian veins; both ducts have double semilunar valves at their orifices, preventing regurgitation of blood.

Nervous System.

What are the two divisions of the nervous system?

The cerebro-spinal or that presiding over animal life, and the sympathetic, that regulating organic life.

Describe the structure of the nervous tissue.

It is composed chiefly of two structures, the gray or vesicular originating impulses and receiving impressions; and white or fibrous, conducting impressions; in the sympathetic system is found a third structure, gelatinous nerve-tissue; seventy-five per cent. of nerve-tissues is composed of water, the remainder being albumen, phosphorized-fat, and salts.

Describe the microscopic structure of the white nervetissue.

It is formed of tubular fibres each consisting of a central axiscylinder, surrounded by the white substance of Schwann, the whole enclosed by the tubular membrane or primitive sheath. A bundle of these fibres invested by a fibro-areolar membrane, the perineurium (neurilemma), constitutes a nerve, receiving a special blood-supply by the vasa nervorum; the gelatinous variety consists of finely granular fibrillæ enclosed in a sheath-by some these are not considered to be nerves.

Describe the gray or vesicular nerve-tissue.

This consists of large granular cells containing nuclei and nucleoli, ovoid, or with one or many processes (unipolar, multipolar), some of which become continuous with an axis-cylinder.

How do nerves terminate?

Peripherally sensory nerves end in minute plexuses, end-bulbs, tactile corpuscles, and Pacinian corpuscles; in the special organs they end in cells and in other not well ascertained ways; motor nerves end peripherally in plexuses or by "motorial end plates."

The central terminations are not well understood.