3T2 LYMPH AND LYMPHATIC GLANDS. [CH. xxn. 



CHAPTER XXII. 



LYMPH AND LYMPHATIC GLANDS. 



As the blood circulates through the capillary blood-vessels 

 some of its liquid constituents exude through the thin walls of 

 these vessels, carrying nutriment to the tissue elements. This 

 exudation is called lymph ; it receives from the tissues the pro- 

 ducts of their activity, and is collected by the lymph channels, 

 which converge to the thoracic duct the main lymphatic vessel 

 and thus the lymph once more re-enters the blood-stream near 

 to the entrance of the large systemic veins into the right auricle. 



Lymph is a fluid, w r hich comes into much more intimate relation- 

 ship with metabolic processes in the tissues than the blood ; in 

 fact, there is only one situation the spleen where the blood 

 comes into actual contact with the elements that is, cells, fibres, 

 &c. of a tissue. 



Composition of Lymph. 



Lymph is alkaline; its specific gravity is about 1015, and after 

 it leaves the vessels it clots, forming a colourless coagulum of 

 fibrin. It is like blood-plasma in composition, only diluted so far 

 as its proteid constituents are concerned. This is due to the fact 

 that proteids do not pass readily through membranes. The 

 proteids present are called fibrinogen, serum globulin, and serum 

 albumin ; these we shall study with the blood-plasma. The salts 

 are similar to those of blood-plasma, and are present in the same 

 proportions. The waste products, like carbonic acid and urea, 

 are more abundant in lymph than in blood. The total amount of 

 solids dissolved in lymph is about 6 per cent., more than half of 

 which is proteid in nature. 



When examined with the microscope the transparent lymph is 

 found to contain colourless corpuscles, which are called lymphocytes ; 

 these are cells with large nuclei and comparatively little proto- 

 plasm. They pass with the lymph into the blood, where they 

 undergo growth, and are called leucocytes. 



All the lymphatics pass at some point of their course through 

 lymphatic glands, which are the factories of these corpuscles. 

 Lymphocytes also pass into the lymph stream wherever lymphoid 

 tissue is found, as in the tonsils, thymus, Malpighian bodies of 

 the spleen Peyer's patches, and the solitary glands of the intestine. 



