76 F. O. SCHMITT VOL. 4 (1950) 



Recent experiments suggesting that axoplasm may be continuously moving peri- 

 pherally from the cell body in the normal neuron^'' ^ have stimulated renewed interest 

 in the colloidal properties of the axon as they concern trophic phenomena. It seems 

 probable that application of the thin sectioning technique may prove valuable in 

 studying axon structure with the electron microscope and that such studies may throw 

 light on the physical basis of trophic processes. 



The axons of fresh fibres offer little promise for X-ray diffraction studies because 

 of their high water content. It was estimated that the axon proteins of the squid giant 

 fibre account for only 3 or 4% of the wet weight of the fibre^^. Dried frog, lobster and 

 crab nerves show equatorial diffractions at about 11 A. It is probable that these diffrac- 

 tions arise from connective tissue because alcohol-dehydrated axons isolated from squid 

 giant fibres showed only two disoriented rings at about 4.7 and 10 A, characteristic of 

 denatured protein^^. These patterns are similar to those obtained from fibres spun from 

 axis cylinder protein. These X-ray investigations of axon structure were not exhaustive 

 and, in view of current electron microscope results, warrant further careful study. 



From the above account it is clear that the problem of structure analysis in nerve 

 is a formidable one. It is particularly challenging because of the high sensitivity of the 

 colloidal organization to physical or chemical manipulation and because the chemical 

 reactions underlying the physiological process are completely unknown. 



There can be little doubt that X-ray and electron microscope techniques, if suffi- 

 ciently acutely applied, are capable of penetrating to or near the molecular level in 

 nerve as has already been accomplished in the case of contractile tissue. Hardly more 

 than a beginning has been made thus far. Progress with the morphological problem 

 would be greatly accelerated if the chemical properties of the nerve proteins were known. 

 The biochemical problem is itself quite formidable bur there is no reason to doubt that 

 it would yield if subjected to a concerted attack by modern methods of isolation and 

 characterization. The bioelectric aspects have attracted the best efforts of many com- 

 petent investigators and their analysis is still proceeding. The time has come for an 

 equally concentrated attack upon the morphological, biochemical and enzymological 

 aspects. Only thus may we expect to make significant progress with a problem as com- 

 plex as that of nerve function. 



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