ULTRASTRUCTURE AND HI STOPHYSI OLOG Y OF MEMBRANES 9 



in mesaxons. Thus most of the nerve fibers in a given fascicle are not 

 directly in contact with the extracellular environment. Figure 6 helps 

 demonstrate this relationship. At least five nerve fascicles are evident 

 containing numerous small axons. The regions designated by the (K) 

 indicate two mesaxons which represent continuity with the extracellular 

 spaces (Es). In direct contrast, all other nerve fibers thus far examined, 

 show an individual mesaxon for each individual unmyehnatcd nerve fiber 

 (compare Figs. 5 and 6 with Fig. 12). Here a single mesaxon can serve 

 several hundred nerve fibers in a single fascicle. Since thece membrane 

 relationships may have important bearing on ion movements between the 

 axoplasm and the extracellular spaces the structural differences have been 

 somewhat labored. Text-figure 11 is a diagramatic representation of the 

 organization of the olfactory nerve described by de Lorenzo in 1956 and 

 1957 and confirmed by Gasser. 



MESAXONS 



Text-fig. IT. Schematic representation of the organization of the fila 

 olfactoria based upon our observations with the electron microscope. 



