60 The Lyrriphocyte and Lymphocytic Tissue 



In small lymphocytes the Golgi zone is usually to one side of the centro- 

 sphere. In fortuitous sections (Fig. 4-7) the Golgi zone is demonstrable as a 

 series of flattened sacs, circular or oval profiles of vacuoles, and larger 

 vacuoles with clear (enter and indistinct outlines. The flattened sacs have a 

 curvature which partly encircles the centrosphere. The centrosphere itself 

 is generally lucid but of irregular density and usually contains no clearly 

 defined structures except the centrioles. Occasionally one (Fig. 4-7) or, 

 more rarely, two centrioles may be observed within the centrosphere. The 

 centriole, when visualized in cross section, is seen to be composed chiefly of a 

 circlet of nine rodlets. The electron microscopy of the centrioles, centro- 

 sphere, and associated Golgi zone in blood cells has been described by 

 others.- 1 



Azurophile granules and granules or droplets of high lipoid content are 

 both recognized to be inconstant inclusions of lymphocytes. 1 ' 1 The former 

 are only infrequently seen in electron microscopic preparations (Reference 

 11, p. 121). They are composed of a moderately dense, homogeneous core 

 which is surrounded by a lucid zone. On the outside there is an apparently 

 membranous covering of about the same density as the core. Granules with 

 high lipoid content are very variable in size, shape, and density. Often an 

 inclusion within the granule occupies more than half its area in the micro- 

 graph and may be either denser or more lucid than the core. Occasionally 

 there may be lamination (Reference 11, p. 123) . 



Nicleus 



The nuclear membrane of lymphocytes has no special features, conforming 

 to the pattern of ultrastructure characterizing cells in general (References 1 1 , 

 p. 1 19, and 22) . It is double, with each component tracing an irregularly 

 wavy course. Nuclear pores are present and seem to be more readily demon- 

 strable in the larger cells. The nucleoli of lymphocytes possess no structural 

 organization special to the lymphocyte. 23 Close examination of nucleoli 

 reveals a structureless background somewhat denser than the nuclear sub- 

 strate elsewhere (i.e., in areas of the nucleus not containing a nucleolus) . A 

 heavy population of the dense granules that are characteristic of nucleoplasm 

 fixed by the buffered Os0 4 technique completes the picture. 



Nucleoplasmic density in these Os0 4 preparations is worthy of special 

 notice, since its patternization is a most useful index of the stage of de- 

 velopment of the cell (Reference 11, pp. 261, 281). The dense granules of 

 the nucleoplasm are irregularly distributed against an amorphous back- 

 ground which itself may be subject to considerable density variation, 

 especially in mature cells. In very young cells such as the myeloblasts, mono- 

 blasts, and lymphoblasts of the peripheral blood of leukemic patients, both 



