THE BLOOD AND LYMPH. 133 



affinity for neutral anilin-dyes (Fig. 113, / and g). This variety 

 constitutes about 72 per cent, of the total number of leucocytes, and 

 is probably produced chiefly in the red marrow of the bones. They 

 possess the power of executing amoeboid movements and incor- 

 porating foreign particles. 



2. The lymphocytes, with a single round nucleus and a little clear 

 cytoplasm around it. These leucocytes are of about the same size 

 as the red blood-corpuscles (Fig. 113, b). They are derived from 

 the lymphadenoid tissue in the lymph-nodes and other situations, 

 and appear to be capable of only feeble amoeboid movement. They 

 constitute about 23 per cent, of the total number of leucocytes in 

 normal blood. 



3. The large mononuclear leucocytes, which are larger than the 

 red corpuscles and have oval nuclei surrounded by clear cytoplasm 

 (Fig. 113, c). This variety has also received the name " myelocyte," 

 on the probably correct assumption that they are derived from the 

 red marrow of the bones. They are capable of passing through 

 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. 110, d), 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. (/., eosin. These are frequently seen in unusual numbers 

 around inflammatory foci or in tissues undergoing involution ; e. g. y 

 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 role 



