TYPICAL STRUCTURE OF ORGANS 



39 



received from the blood, while the 

 the lymph substances discharged 

 from the cells. The lymph thus 

 becomes the means of communi- 

 cation, the middleman, between 

 the living cells of the organs 

 and the nourishing blood, and 

 forms the immediate environment 

 of the cells themselves. In other 

 words, the cells of muscles, glands, 

 and other organs live in lymph, just 

 as the human body as a whole 

 lives in air, or a fish in water. 



12. The lymphatics. Besides 

 the veins, which convey blood 

 away from an organ, a second 

 system of tubes or vessels passes 

 out through the capsule. These 

 tubes arise in the lymph spaces 

 of the connective tissue and 

 unite with similar tubes from 

 other regions to form larger and . 

 larger trunks, known as lym- 

 phatics, which ultimately form 

 one or two great trunks and 

 open into the great veins near 

 the heart (see Fig. 30). Through 

 these direct outlets the surplus 

 lymph of the organ flows in a 

 varying but for the most part 

 continuous stream. This flow 

 of lymph away from an organ 

 is of the very greatest impor- 

 tance in maintaining the normal 

 environment of the cells. 



blood, in turn, takes from 



FIG. 30. The two main lymphatic 



trunks (in white), with their 



openings into the great veins 



near the heart 



The larger of these trunks that 

 on the left side and known as 

 the thoracic duct returns all the 

 lymph except that from the right 

 side of the head and neck and the 

 right arm and shoulder region 



