126 NORMAL HISTOLOGY. 



transitional forms until they acquire the characters of the polynuclear 

 neutrophilic leucocytes described above. The large mononuclear 

 leucocytes, together with the transitional forms, make up about 3 

 per cent, of the normal number of leucocytes. 



4. The eosinophilic leucocytes (Fig. 103, d) 9 also larger than the red 

 corpuscles, with irregular, polymorphic nuclei, and a cytoplasm 

 containing relatively large granules which have an affinity for acid 

 dyes ; e. g., eosin. These are frequently seen in unusual numbers 

 around inflammatory foci or in tissues undergoing involution; e. #., 

 in the connective tissue of the breast when lactation is suspended. 

 Their significance is not understood, but they appear to be derived 

 from the red bone-marrow. They constitute from 1 to 2 per cent, 

 .of the total number of leucocytes. 



5. Basophilic leucocytes, occasionally met with, which are charac- 

 terized by the presence of granules in the cytoplasm having a 

 .special affinity for basic anilin-colors. These cells have also 

 received the names " mast-cells" and plasma-cells, but the latter 

 term is indefinite, having been applied to a number of cells of 

 .different nature. 



The blood-plates are colorless round or oval discs, about one- 

 fourth the diameter of the red corpuscles. Their function has not 

 been definitely determined, but it is thought that they may play a rdle 

 in the production of fibrin, perhaps by the liberation of fibrin-ferment. 



Minute globules of fat are occasionally present in the blood, 

 -especially during digestion. 



The lymph, like the blood, consists of a fluid portion, the plasma, 

 and corpuscles held in suspension. 



The plasma, as would be anticipated from its origin, is very 

 similar in composition to that of the blood. 



The corpuscles are, for the most part, identical with the small 

 leucocytes (lymphocytes) of the blood, which derives its supply of 

 those cells from the lymph flowing into it. 



The chyle is the lymph found in the lacteal lymphatics during 

 .digestion. When absorption of the products of digestion is in 

 progress this lymph contains a great number of globules of fat, 

 ome so minute as to be barely visible under the microscope. In 

 the intervals between absorption this lymph does not differ from 

 that found in the other lymphatics of the body. 



Fibrin may present the appearance of a delicate network of ex- 

 tremely fine fibres, somewhat resembling a cobweb (Fig. 268), or these 



