LAMELLAR SYSTEMS 



141 



equivalent configuration of the native filaments. The images re- 

 corded are similar to transverse sections of dendrites, or to the 

 cross-sectioned tobacco mosaic virus particles described earlier 

 ( Fernandez-Moran and Schramm, 1958). These observations may 

 be of interest in connection with the extensive chemical and physico- 

 chemical studies of the macromolecular constituents of axoplasm 

 which are now being carried out by Davison, Taylor, and Schmitt 



Fig. 13. Myelin sheath-axon segment from transverse section of frog sciatic 

 nerve, showing (a) dense body frequently observed in the axon, v/ith (b) in- 

 ternal layered structure exhibiting a period of 40 to 50 A. Osmium-cryofixation 

 preparation after rapid freezing in Freon 22-liquid nitrogen, (a) X 80,000. 

 (b) X 450,000. 



(Schmitt, 1959). Another component which is encountered in 

 osmium-cryofixation specimens more frequently than in the stand- 

 ard preparations, is represented by dense bodies of 0.2 yu, to over 1 /x 

 in diameter. As shown in Fig. 13, many of these bodies exhibit a 

 regular layered fine-structure with a period ranging from 30 to 40 A. 

 The bodies are more numerous in certain regions of the nerve fiber, 

 particularly in the vicinity of the nodes. 



