HOBER: THE MEMBRANE THEORY 389 



with one to three double bonds, e.g., in oleic, linolic, linoleic, arachi- 

 donic, nervonic, and oxynervonic acids. These long carbon atom 

 chains of the lipoids, lecithin, kephalin, sphingomyelin, and cerebrosides 

 seem to be existent, not only in the massive sheath of the myelinated 

 nerve fibers, but, according to Young and Francis Schmitt,^^ also in 

 the unmyelinated fibers of crabs and cephalopods (for instance, the 

 squid nerve) , where the thickness of the sheath has been found to be 

 as small as one per cent of the diameter of the axon, i.e., about 5/i, 

 compared to 25 per cent of the diameter in vertebrates, as shown by 

 Pumphrey and Young (plate 1). In the sheath of the unmyelinated 

 fibers, the lipoids, though often not demonstrable by the customary 

 staining with osmium tetroxide, can be detected with polarization 

 optics (Bear and F. 0. Schmitt-^). 



Now, looking upon the excitatory process from the standpoint of the 

 old "Stromchen theory" of Hermann,^* it is at the boundary between the 

 stimulated altered and the adjacent, unaltered region that small local 

 circuit currents arise, flowing out of the unaltered region, which then 

 secondarily gets altered as in a catelectrotonus, and flowing in at the 

 originally stimulated region, which, thus, is inactivated as in an anelec- 

 trotonus. Catelectrotonus, however, as mentioned before, means soften- 

 ing the colloidal membrane and dispersing its structural aggregates by 

 way of potassium and chloride ions and depolarization of the normal 

 resting membrane. Anelectrotonus, on the other hand, means condensa- 

 tion and re-polarization. The aforementioned increase of concentration 

 of potassium, which happens to be produced in the membrane by the 

 outflowing current, may then serve to liberate in the nerve membrane, 

 directly, some of the nonpolar-polar anions, as, according to the well- 

 known studies of G. L. Brown and W. Feldberg," acetylcholine is liber- 

 ated by even a very small surplus of potassium (amounting to not more 

 than 0.01 per cent) in the perfused ganglion cells, where it normally 

 is fixed in a nondiffusible state. However, the mechanism of this re- 

 lease is by no means clearer than that just suggested for the nonpolar- 

 polar anions. Alternatively, the nonpolar-polar anions could possibly 

 be liberated, indirectly, by an activation of lecithase A, an enzyme 

 occurring in nerve tissue, which is known to set free the unsaturated, 

 but not the saturated, fatty acids of the lipoid molecules. ^^ 



These are speculations, it is true. If, however, we refer them to the 

 giant axon of the cephalopods, which was studied, in recent years, 

 with most diversified and modern methods, it means that probably 

 the alterations are bound up with the thin surface membrane which 

 wraps up the voluminous column of axoplasm, and that this fine mem- 



