330 THE HUMAN BODY. 



subclavian. The trunk on the right side is much smaller 

 than the other and is known as the "right lymphatic duct." 

 It collects lymph from the right side of the thorax, from 

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

 The lymph from all the rest of the Body is collected into 

 the thoracic duct. It commences at the upper part of the 

 abdominal cavity in a dilated reservoir (the receptaculum 

 chyli), into which the lacteals from the intestines, and the 

 lymphatics of the rest of the lower part of the Body, open. 

 From thence the thoracic duct, receiving tributaries on its 

 course, runs up the thorax alongside of the aorta and, pass- 

 ing on into the neck, ends on the left side at the point 

 already indicated; receiving on its way the main stems 

 from the left arm and the left side of the head and neck. 

 The thoracic duct, thus, brings back much more lymph 

 than the right lymphatic duct. 



The Serous Cavities. These are great dependencies of 

 the lymphatic system and may be regarded as large lacunae. 

 Each of them (peritoneal, pleural, arachnoidal and peri- 

 cardiac) is lined by a definite epithelioid layer of close-fit- 

 ting, hexagonal cells. At certain points, however, openings 

 or stomata occur, surrounded by a ring of smaller cells, and 

 leading into tubes which open into subjacent lymphatic 

 vessels. The liquid moistening these cavities is, then, really 

 lymph. 



The Lymphatic Glands. These are roundish masses in- 

 terposed, at various points, on the course of the lymph-ves- 

 sels. They are especially numerous in the mesentery, groin, 

 and neck. In the latter position they often inflame and 

 give rise to abscesses, especially in scrofulous persons; and 

 still more often enlarge, harden, and become more or less 

 tender, so as to attract attention to them. In common par- 

 lance it is then frequently said that the person's " kernels 

 have come down," or that he has " waxing kernels." Eacli 

 lymphatic gland is enveloped in a connective-tissue capsule, 

 and is pervaded by a connective-tissue framework. In the 

 meshes of this lie numerous lymph corpuscles, which appear 

 to multiply there by division. " Afferent " lymphatic ves- 

 sels open into the periphery of the so-called gland, and ef- 



