THORACIC DUCT 2 23 



into the tissue spaces, and this is the source of its nutritive principles. 

 Waste matters are added as the result of the activities of the tissues 

 themselves; they represent the "tissue waste." This fluid, con- 

 veyed by lymph-capillaries to lymph-vessels, is carried to lymph 

 glands, where it gathers the lymph corpuscles which float in it. 



Lymph nodes or lymph glands are small round or oval bodies 

 of a reddish color, varying in size from that of a pin head to a 

 small bean, and intersecting the lymph vessels in certain regions of 

 the body. They are numerous in the neck, axilla and groin, also 

 in the thorax and abdomen. 



A lymph gland is invested with a thin but firm capsule (fibro- 

 muscular) which sends septa or partitions into the interior, to 

 support the gland substance in small compartments. The gland 

 (lymphoid or adenoid) substance lies loosely in this capsule and in 

 the compartments, leaving spaces for the passage of lymph around 

 the different portions and around the whole. It contains great 

 numbers of young corpuscles, which are added to the lymph stream 

 as it washes through the gland, and appear later as the lymphocytes 

 of the blood. 



Lymph is brought to the glands by afferent lymph vessels, 

 usually several for each gland. After flowing through the various 

 spaces in and around the gland substance, it leaves by efferent 

 vessels, which unite to carry the stream on its way toward the 

 large veins. 



A specimen taken from an efferent vessel and examined under the micro- 

 scope will show a greater number of lymphocytes than one taken from an 

 afferent vessel. 



The largest lymph vessel is called the thoracic duct (p. 189). 

 It is about 1 8 inches long, having an average diameter of a small 

 goose-quill. It begins at the second lumbar vertebra, in a little 

 pouch called the receptacle of the chyle (or receptaculum chyli] and 

 runs up behind the aorta, through the diaphragm. It then con- 

 tinues upward through the thorax to the level of the seventh cer- 

 vical vertebra, where it arches over to open into the left sub- 

 clavian vein (at the junction with the left internal jugular). Thus 

 the lymph and chyle join the current of venous blood on its way to 

 the heart for circulation and distribution. 



The right lymphatic duct is a short vessel, a half inch in 

 length, which opens into the right subclavian vein at the junction 



