142 



SUBCELLULAR PARTICLES 



£j/ 





4*> 



luT 



Fig. 10. Electron micrograph of lysosoine-rich fraction. Unpublished picture taken by 

 Dr. Novikoff in collaboration with Dr. Claude. Preparation similar to that of figure 9. X 37)500. 



are surrounded by a single membrane; others show one or more hiternal cavities, 

 sometimes Hned with a broad layer of denser material, or contain clumps of such 

 material. Most of them have in common a fine granular texture, made of small 

 granules of high electron density, reminiscent of the iron micelles described by 

 Farrant (32) in crystalline ferritin. It has indeed been established that lysosome- 

 rich fractions contain more easily detachable iron (ferritin?) than the other par- 

 ticulate fractions (23). The results of these determinations suggest that up to 

 10 per cent of the cell ferritin may be associated with lysosomes or related par- 

 ticles, most of the remainder being in the final supernatant. They are therefore 

 not in conflict with the recent observations of Kuff and Dalton (57), who have 

 identified ferritin in the cytoplasmic ground substance and recovered it to a 

 large extent in the soluble fraction. It should finally be noted that dense bodies 

 lacking the ferritin-like granules were also occasionally found in our fractions 

 (fig. 10). These appear to correspond to the microbodies described by Rouiller 

 and Bernhard (83). 



