246 ABSORPTION LYMPH AND CHYLE 



more superficial of these layers is composed of a rich plexus of small 

 vessels, and beneath the mucous membrane is a plexus consisting of 

 vessels of larger size. The superficial plexus is very rich in the mixed 

 structure which forms the lips and the glans penis, and around the 

 orifices of the mouth, the nares, the vagina and the anus. There are 

 certain mucous membranes in which the lymphatics have never been 

 injected. In the serous membranes lymphatics have been demon- 

 strated in great abundance. Lymphatics have also been observed 

 taking their origin in the voluntary muscles, the diaphragm, the heart 

 and the non-striated muscular coats of the hollow viscera, although 

 their investigation in these situations is difficult. 



Lymphatics are found coming from the lungs in great numbers. 

 These arise in the walls of the air-cells and surround each pulmonary 

 lobule with a close plexus. The deep vessels follow the course of the 

 bronchial tubes, passing through the bronchial glands and the glands at 

 the bifurcation of the trachea, to empty into the thoracic duct and the 

 great lymphatic duct of the right side. 



In the glandular system, including the ductless glands, and in the 

 ovaries, the lymphatic vessels are, as a rule, more abundant than in any 

 other parts of the body. They are especially abundant in the testicles, 

 the ovaries, the liver and the kidneys. 



The lymphatic vessels from the superficial and deep portions of the 

 head and face on the right side, and those from the superficial and deep 

 portions of the right arm, the right half of the chest, and the mammary 

 gland, with a few vessels from the lungs, pass into the great lymphatic 

 duct (ductus lymphaticus dexter), which empties into the venous system 

 at the junction of the right subclavian with the internal jugular. This 

 vessel is about an inch (25.4 millimeters) in length and ^ to i f an 

 inch (2 to 3 millimeters) in diameter. It is provided with a pair of semi- 

 lunar valves at its opening into the veins, which effectually prevents the 

 ingress of blood. The vessels from the inferior extremities and those 

 from the lower portions of the trunk, the pelvic viscera, the abdominal 

 organs generally and the left half of the body above the abdomen empty 

 into the thoracic duct. 



In their course, the lymphatics pass through the small, flattened, oval 

 bodies, called the lymphatic glands, or nodes, which are abundant in the 

 groin, the axilla, the pelvis and some other parts. Two to six vessels, 

 called vasa afferentia, penetrate each node, having first broken up into 

 a number of smaller vessels just before they enter. They pass out 

 by a number of small vessels which unite to form one, two or three 

 trunks, usually of larger size, than the vasa efferentia. The vessels 

 which thus emerge from the glands are called vasa efferentia. 



