io6 



PHYSIOLOGY FOR BEGINNERS 



numerous valves, formed like the valves in veins, which allow 



the flow of the lymph in 

 the right direction only. A 

 valve guards the opening 

 of the duct into the jugular 

 vein. The lymph flows 

 along because the pressure 

 where it is constantly 

 being formed from the 

 capillaries is greater than 

 is the pressure in the great 

 veins where it is poured 

 into the blood, and also 

 because any movement of 

 the body by pressure on 

 the tissues drives the lymph 

 past the valves which pre- 

 vent its return. 



Lymphatic Glands. 

 Along the course of the 

 lymphatics small solid 

 bodies are met here and 

 there which vary in size, 

 some of the largest being an 

 inch or more in length, and 

 are often bean - shaped. 

 Lymphatics open intothem 

 on one side and leave them 

 on the other. These are 

 called lymphatic glands. 

 Eachconsistsofameshwork 

 of fine connective tissue, 

 holding in its meshes a 



FIG. 50. The thoracic duct. 



large number of colourless 



, .part of ribs ; , receptaculum chyli ;/>, trunk corpusc l es closely packed 

 of thoracic duct, opening at c into junction _, . . 



of left jugular (/) and left subclavian (,>) together. The Colourless 



veins. The connection of these veins with corpuscles Or leUCOCytCS as 



the superior vena cava (A) has been cut they are called, are smaller 



across to show the thoracic duct behind faa.n the Colourless COf- 

 it ; d. lymphatic glands in the lumbar . 



regions puscles of the blood; in 



