FIG. 2. A small region from the cytoplasm of a normal rat liver cell. A section 

 of the margin of the nucleus (TV) is at the upper left. It is separated from the 

 cytoplasm by the nuclear envelope (ne), which in the profile included within the 

 section, shows several pores (arrows). Two structurally dissimilar membrane sys- 

 tems dominate the fine structure of the cytoplasm. The most prominent of these, 

 appears in long, slender profiles representing vertical thin sections through large 

 lamellar vesicles 50 to 75 millimicrons thick. The membranes limiting these struc- 

 tures are studded with dense particles (ribosomes) and because of these this form 

 of the endoplasmic reticulum is referred to as the rough ER irer) . Continuous 

 with this rough form (see arrow for point of continuity), is another type of retic- 

 ulum composed for the most part of tubules, interconnected in a three-dimensional 

 lattice. In liver cells this agranular or smooth form of the reticulum (ser) is always 

 associated with glycogen. The matrix of the cytoplasm in which these structures 

 are embedded appears homogeneous although in some instances, even in liver cells, 

 there is occasional evidence of bundles of fine, filamentous elements. Where the 

 cisternae of the rough ER are cut obliquely, the distribution of ribosomes on their 

 surfaces is depicted. Beside ribosomes not attached to membranes, the matrix con- 

 tains resolvable glycogen granules (gl), and sometimes ferritin particles. The liver 

 cell, which has become a classical object for cytochemical investigations, has one 

 of the most complex of cytoplasms, related presumably to the complex physiolog- 

 ical role of these cells. Nearly all the organelles and systems found in any cell are 

 represented. It serves as a useful background for the somewhat simpler but diverse 

 morphologies illustrated in the other figures. Magnification: 27,000 X. 



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