BLOOD 2OI 



Plasma is the fluid intercellular substance of the blood. It contains 

 various granules, some of which are small fat drops received from the 

 thoracic duct. Others occurring in variable quantity are refractive parti- 

 cles, not fatty, either round or elongated; they are known as haemato- 

 conia (or hsemoconia). In ordinary sections the plasma appears as a 

 granular coagulum. In the process of clotting, fibrin forms from the 

 plasma, and with the entangled corpuscles, it constitutes the blood-clot; 

 the fluid which remains is the serum. The process of fibrin formation 

 is of considerable histological interest, owing to a possible analogy with 

 fibril formation in connective tissue. 



LYMPH. 



The contents of the lymphatic vessels is called lymph. This fluid 

 is not identical with plasma, or with tissue fluid, yet all three are similar. 

 Nutrient material passes from the plasma into the tissue fluid and 

 thence to epithelial cells; and in return the products of epithelial cells 

 enter the tissue fluid from which they may be taken over either into 

 the plasma or lymph, first passing through the endothelial walls of the 

 vessels. Thus in the intestine much of the absorbed fat is transferred 

 across the tissue spaces to the lymphatic vessels (lacteals) within which 

 it forms a milky emulsion known as chyle. This form of lymph mingles 

 with other varieties coming from the various parts of the body, and 

 together they are poured into the plasma at the jugulo-subclavian junction. 

 Histologically lymph appears as a fine coagulum, containing lymphocytes 

 and large mononuclear phagocytic cells. The cells are not abundant. 

 Occasionally other forms of blood corpuscles are found in lymphatic 

 vessels, but the lymphocytes greatly predominate. 



