CHAPTEE 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 products 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, which 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, etc. 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 protoplasm. 

 They pass with the lymph into the blood, where they undergo 

 growth, and are called leucocytes. 



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