ANATOMY IN A NUTSHELL. 117 



but much thinner opposite the joints. Each sheath is lined by a synovial mem- 

 brane, which is reflected upon the tendons. The synovial sheaths for the ten- 

 dons of the thumb and little finger are continuous with the two synovial bursa' 

 beneath the anterior annular ligament, but those for the intervening digits 

 terminate in a sac near the metacarpophalangeal articulation. The outer por- 

 tion (thenar fascia) covers the ball of the thumb. Proximally it is attached to 

 the anterior annular ligament, the tendons of the Palmaris brevis and apo- 

 neurosis from the tendons of the Extensor ossis metacarpi pollicis. It contin- 

 ues distally with the ligamenta vaginalia of the Flexor longus pollicis. The inner 

 portion or hypothenar fascia, is triangular with the apex proximally and at- 

 tached to the anterior annular ligament and deep fascia of the forearm at the 

 inner side of the wrist : distally it is covered above by the Palmaris brevis. 

 (Plate XXX.) 



LESSON XXXI. 



Besides the arterial, venous and capillary circulation there is a lymphatic 

 circulation extending over the body by beginning in microscopical spaces and 

 extending until they form lymphatic vessels. These vessels are enlarged by 

 receiving radicles or tributaries in a like manner to the veins. Along the course 

 of the lymphatic vessels are lymphatic nodes, sometimes called glands. There 

 are in the neighborhood of seven hundred of these nodes. They are situated 

 principally in the abdominal and thoracic cavities. In the upper extremity 

 they are found no farther than the elbow. In the lower extremity they are 

 found no farther than the popliteal space, as a rule: however, a few may be 

 found on the anterior tibial artery. These nodes manufacture the white blood 

 corpuscles. There are four other places in the body where they are manu- 

 factured. viz.. spleen, thymus gland, thyroid gland and the red marrow of b 



The lymph of all the body, except the right side of the head, the right side 

 of the thorax, the right arm, and the upper surface of the liver collects into a 

 large duct, the left lymphatic or thoracic duct. It is called thoracic duct be- 

 cause it passes through the thorax. It is about fifteen or eighteen inches long. 

 It begins in front of the second lumbar vertebra where it is enlarged (recep- 

 taculum chyli) and extends through the thorax, through the superior opening 

 of the thorax, and empties into the left subclavian or innominate vein. 



The heart is the main factor in the circulation of the lymph. The other 

 factors will be learned in physiology. The lymphatic vessels and nodes, like 

 the veins of the arm, are in two sets, a superficial and deep set. After the blood 

 has passed through the arteries and capillaries, nourishing the various parts, it 

 comes back by means of the vein.-. 



The superficial veins of the distal extremity receive the name radial, an- 

 terior and posterior ulnar, and median. They lie between the two layers of 

 the superficial fascia. (Plate XXXVII.) 



The anterior ulnar is formed by a network of veins at the anterior and ulnar 

 side of the hand and wrist. It extends on this aspect of the forearm t<> the 

 bend of the elbow where it joins the posterior ulnar to form the common ulnar. 



