ANGEIOLOGY. 103 



but more delicate than that of veins ; they liavc three coats, but the middle, 

 as in the veins, is thin, and wants the elastic lamina. 



The lymphatic or conglobate glands are very numerous both in the 

 extremities and in the trunk ; their size varies from that of a small currant 

 to that of an almond ; the largest are in the groins and in the roots of the 

 lungs. Their form is round, or irregular and lobulated. 



The Lymphatic Vessels of the Lower Extremities. These are superficial 

 and deep. The superficial commence from the toes, rise along the dorsum 

 of the foot, and pass up the leg in two divisions, which, however, frequently 

 communicate : one, the internal group, passes in front of the inner ankle, 

 and keeps parallel and close to the great saphena vein ; these branches 

 ascend to the groin, and pass through the inferior superficial gland into the 

 external iliac gland. The external set of superficial lymphatics ascend 

 behind the inner ankle, accompany the external saphena vein to the ham, 

 pass through the glands there situated, and join the deep lymphatics of the 

 limb. 



The lymphatics of the trunk and viscera are very numerous and exceedingly 

 complicated. The absorbents of the small intestines are either lymphatics 

 or lacteals ; the former arise in the subserous tissue, the latter in the sub- 

 mucous tissue and in the villi. The lacteals proceed at once from the intes- 

 tine into the mesentery and its glands: they take up the chyle and pour it 

 into the thoracic duct. 



The thoracic duct, great or left, is the common recipient of the absorbents 

 not only of the infra-diaphrngmatic portion of the body, but also of those 

 of the left side of the chest, head, neck, and left arm. It commences by the 

 confluence of a variable number of branches, in a common reservoir or 

 dilatation called receptacidnvi chyli, which is placed to the right and some- 

 what behind the aorta, and rising into the neck, arches forwards and down- 

 wards, opposite the seventh cervical vertebra, and empties into the angle 

 between the left subclavian and jugular veins, protected by a pair of valves 

 against regurgitation from these vessels. 



The head, face, and neck are well supplied with lymphatics. Ten, how- 

 ever, occur in the cranium, and none have as yet been detected in the brain. 

 En the upper extremity, the superficial lymphatics commence from the 

 fingers and the back part of the hand, and accompany the subcutaneous 

 veins. Tiie deep lymphatics follow the individual blood-vessels, reach the 

 axillary glands, and receive various branches. On the left side they accom- 

 pany the subclavian vein and join the descending portion of the thoracic 

 duct. On the right side, the axillary or subclavian lymphatics, joined by 

 the right cervical, form a short trunk about an inch in length, termed the 

 right lymphatic duct. This trunk opens into the angle between the right 

 subclavian and jugular veins ; it is the termination of the lymphatics of the 

 right arm, right side of the thorax, and of the head and neck, 



PL 136, ßg. 14', superior vena cava; % azygos vein: ', thoracic duct', 

 *, portion of the pelvic plexus ; ", external iliac do. ; ', lumbar do. ; ', recep- 

 taculum ; °, point of union of the chyliferous vessels of the intestinal canal, 

 with the thoracic duct; '■', intercostal lymphatics; '"•"', deep lymphatics of 



809 



