56 The Lymphocyte and Lymphocytic Tissue 



balances interpretative difficulties. The gradually accumulating knowledge 

 of ultrastructure in lymphocytes and other blood cells 111 may now be col- 

 lated with the classic evidence obtained from the light microscope 16, 1T to 

 formulate new concepts of hematologic organization. 



RESULTS 



Lymphocytes in electron microscopic preparations may present consider- 

 able variations in general appearance (Reference 11, pp. 64-77). but a 



y 



nu 



,er 



Fig. 4-1. Lymphocyte; normal human blood. The generally clear cytoplasm 

 and sparse profiles ot endoplasmic reticulum (er) and nucleolus (tin) are all 

 characteristic. (X 8600) 



Fig. 4-2. Lymphocyte; normal human blood. A nucleolus (nu) is visible, and 

 profiles of endoplasmic reticulum are visible (er) in the generally clear cyto- 

 plasm, (x 9500) 



distinct structural type is recognizable (Figs. 4-1, 4-2, 4-3, 4-10) . The 

 nucleus is often large and well rounded, but slight variations of contour may 

 become exaggerated due to the thinness of the section. The nucleoplasm 

 shows two different densities (Figs. 4-10, 4-11) , the dark and the light areas 

 being mixed haphazardly with each other without the definite patternization 

 that occurs in other mature blood cells (Reference 11, pp. 45, 57, 78) . One 

 or more nucleoli may be present, depending on the plane of section. The 

 outstanding characteristic of the cytoplasm is its clarity, which is conspicuous 

 when compared to that of other cell types. Among the formed elements the 

 rat Iter large mitochondria are conspicuous. The small circular or oval pro- 



