Fig. 5. Endothelial cell of a blood capillary (rat heart muscle). 1 = lumen of 

 capillary; cm = cell membrane; bb = brush border; v = vesicles inside cell 



which are in many cases invaginations of cell membranes. 



Magnification = 43,333. (Palade, 1956a. Reproduced by permission of the 



Editors, J. biophys. biochem. Cylol.) 



