LYMPHATIC CAPILLARIES 699 



capillaries form a fairly regular ring which has been called by Teichmann a circulus lymphaticus. 



At the various orifices of the body, the skin plexuses go over into the mucous plexuses, 

 forming anastomoses with them. Throughout the entire alimentary trad, including the nasal 

 cavities, the lymphatic capillaries form extensive plexuses which are in many places divided 

 into a superficial plexus in the mucosa and a deeper plexus in the submucosa. In portions pro- 

 vided with a peritoneal covering, there is a third rich subserous plexus. In the tongue and the 

 small intestine the plexus in the mucosa sends out blind cul-de-sacs; in the tongue into the 

 filiform papillae; in the small intestine into the villi. Where muscle is present along the ali- 

 mentary tract, the lymphatics pass between the muscle bundles, but form no plexuses around 

 them. 



The lining of the tracheal and bronchial passages is supplied with a double plexus of lym- 

 phatic capillaries, a mucous and a submucous set, which vary in richness according to the loose- 

 ness of the tissue. In the smaller bronchi but a single layer of capillaries is present, and, ac- 

 cording to Miller, no capillaries are present around the air cells. Plexuses surround the pul- 



FiG. 547. — The Lymphatics of the Scrotum. (After Teichmann.) Showing the transition 

 of the capillaries to the vessels with valves (a, a, a). 



monary arteries and veins. Under the pleura lie rich plexuses which connect with the deeper 

 lymphatics around the veins only in places where the veins reach the surface of the lung. 



Concerning the arrangement of the lymphatic capillaries in the glands derived from the 

 alimentary tract much remains to be learned. 



The salivary glands have been recently studied anew by Aagaard, who has found lymphatic 

 capillaries accompanying the blood-vessels into the interior of the lobules, and forming here 

 irregular plexuses. 



The thyreoid gland contains lymphatic plexuses which lie in relation to the colloid-con- 

 taining alveoli. Direct connection between the lymphatics and the alveoli has lately been 

 described by Matzunaga, but this observation needs verification. The lymphatics are apparently 

 concerned in the absorption of the colloidal secretion, for traces of it have been found in the 

 lymphatics draining the gland. 



Concerning the lymphatics of the parathyreoids nothing is known. 



The course of the lymphatics draining the thymus has been recently described, but the 

 nature of the capillaries in this gland is unknown. 



The lymphatic capillaries of the liver are of great importance, for the lymph which flows 

 from this organ forms a very considerable part of the total lymph which is collected into the 

 thoracic duct. And yet very little is definitely known about the nature and distribution of the 

 lymphatic capillaries in the interior of the organ. In the capsule there is a rich plexus, lying 

 under the peritoneum, in which very large widenings have been described (called by Teichmann 

 "Lymphbehalter"). In the interior rich plexuses surround the branches of the hepatic artery 

 and portal vein (fig. 549), and plexuses have been described accompanying the branches of the 

 portal vein into the lobules. 



The linings of the large bile-ducts and the gall-bladder are provided with a submucous network 

 of lymphatics (Sudler and Clermont). The gall-bladder has also a rich subserous plexus. 



Concerning the lymphatic capillaries of the pancreas Bartels notes briefly that they form 

 richly branched plexuses in the interlobular connective tissues, which surround larger or smaller 

 parts of whole lobules, not the single gland elements. 



The mucous lining of the genito-urinary tract, wherever it has been carefuUy studied 



