62 The Lymphocyte and Lymphocytic Tissue 



series because it is characterized by dark cytoplasm having a generally 

 speckled appearance. The latter is largely traceable to abundant endoplasmic 

 reticulum and to small mitochondria. The nucleoplasm begins its differ- 

 entiation in the monoblast as a narrow dense band just inside the nuclear 

 membrane (Fig. 4-9). The mature pattern is characterized by this band, 

 now wider, and a tew dense areas scattered deeper within the nucleus 

 (Fig. 4-11). Very marked distinction between the lymphocytic and mono- 



Fig 4-10 Lymphocyte; normal human blood. The cytoplasm is clear and the nucleo- 

 plasm has 2 distinct densities which are essentially patternless in their distribution. 

 Compare with the monocyte in Fig. 4-11. (X 9500) 



Fig 4-11 Monocyte; normal human blood. The speckled cytoplasm contains numer- 

 ous small mitochondria and profiles of endoplasmic reticulum (er). The nucleoplasm 

 has 2 distinct densities, the darker of which forms a distinct narrow band under the 

 nuclear membrane, with a lew dense patches deeper in the nucleus The well- 

 developed nucleoplasmic densities of Figs. 4-10 and 4-11 indicate that the cells are 

 mature. (X 8600) 



cytic series is afforded by blood in monoblastic leukemias which contains 

 a' few members of the lymphocytic series (Fig. 4-9) (Reference 11, pp. 285, 

 9 89, 293, 295). Each of these two developmental series in the human leu- 

 kemias is readily identifiable with its own end product, the mature monocyte 

 or lymphocyte of normal peripheral blood. The chief characteristics of 

 mature cells of these two types are summarized below. 



Cells possessing all or most of the above characteristics are very readily 

 identified as either lymphocytes (Fig. 4-10), or monocytes (Fig. 4-11). This 



