CHAPTER IX. 



ABSORPTION. 



THE process of Absorption has, for one of its objects, the introduction 

 into the blood of fresh materials from the food and air, and of whatever 

 comes into contact with the external or internal surfaces of the body; 

 and, for another, the gradual removal of parts of the body itself, when 

 they need to be renewed. In both these offices, i.e., in both absorption 

 from without and absorption from within, the process manifests some 

 variety, and a very wide range of action; and in both two sets of vessels 

 are, or may be, concerned, namely, the Blood-vessels, and the Lymph- 

 vessels or Lymphatics to which the term Absorbents has been also applied. 



THE LYMPHATIC VESSELS AND GLANDS. 



Distribution. The principal vessels of the lymphatic system are, in 

 structure and general appearance, like very small and thin-walled veins, 

 and like them are provided with valves. By one extremity they com- 

 mence by fine microscopic branches, the lymphatic capillaries or lymph- 

 t"/ 'Maries, in the organs and tissues of the body, and by their other ex- 

 tremities they end directly or indirectly in two trunks which open into the 

 large veins near the heart (Fig. 206). Their contents, the lymph and 

 Stifle, unlike the blood, pass only in one direction, namely, from the fine 

 1 tranches to the trunk and so to the large veins, on entering which they 

 are mingled with the stream of blood, and form part of its constituents. 

 Remembering the course of the fluid in the lymphatic vessels, viz., its 

 passage in the direction only toward the large veins in the neighborhood 

 of the heart, it will readily be seen from Fig. 206 that the greater part of 

 the contents of the lymphatic system of vessels passes through a com- 

 paratively large trunk called the thoracic duct, which finally empties its 

 contents into the blood-stream, at the junction of the internal jugular 

 and subclavian veins of the left side. There is a smaller duct on the 

 right side. The lymphatic vessels of the intestinal canal are called lacteals, 

 because, during digestion, the fluid contained in them resembles milk in 

 appearance; and the lymph in the lacteals during the period of digestion 

 is called chyle. There is no essential distinction, however, between lac- 



