

PLATE I. Part of a liver cell (rat) showing the nucleus (n), mitochondria (m), rough surfaced mem- 

 branes (rs) of the endoplasmic reticulum with ribosomes, smooth surfaced membranes (ss), and small 

 vesicles (sv). There is a heavy glycogen deposit (g) in the cytoplasmic matrix. The free surface of 

 the cell shows numerous microvilli (v). 14,000 X- (Courtesy of G. E. Palade.) 



