LAMELLAR SYSTEMS 



135 



Fig. 10. High-resolution electron micrograph of myelin sheath segment 

 from transverse thin section of frog sciatic nerve, shov/ing splitting of interme- 

 diate lines (arrows) in concentric laminated structure, v^^ith an average period 

 of 140 A. Osmium-cryofixation preparation. X 500,000. 



the light microscope at low temperatures (Harris, 1954), tliere is 

 no relevant information available on the interaction of glycerol solu- 

 tions with the submicroscopic organization of tissues. 



Preliminary (unpublished) investigations, carried out in collab- 

 oration with Dr. J. B. Finean at the Venezuelan Institute for Neu- 

 rology and Brain Research in 1957, disclosed characteristic modifica- 

 tions of the low-angle x-ray diffraction pattern of fresh nerve after 

 treatment with glycerol. The changes produced in the diffraction 

 pattern of peripheral nerve myelin from giant toad after equilibra- 

 tion with 30 per cent glycerol in Ringer solution are shown in Fig. 8. 

 Compared with the pattern of fresh nerve, which features a funda- 

 mental period of 174 A, the glycerinated nerve shows general swell- 

 ing of the structure with an enlarged period of 220 A and intensifica- 

 tion ;of the first- and third-order reflections. The relative intensities 

 of the x-ray reflections can be restored to approximately normal ap- 

 pearance by immersion in Ringer solution, but the structure remains 



