GIANT NEURONS OF VISCERAL GANGLION OF APLYSIA 239 



Fig. 8. Cross section of a connective showing a giant axon and the feathery 

 aspect of the abundant glia. CaHbration: 100 micra. 



Schlote (1957) in Helix, there are four or five longitudinal ridges or deep 

 invaginations of the axonal membrane, each occupied by sheath lamellae. 

 These greatly increase the surface of the axon — commonly nearly doubling it. 

 Knowing that this is a normal feature, it can readily be seen in light micro- 

 graphs (Fig. 9) heretofore puzzlingly unconventional. The large fibers have a 

 thick, loosely wound sheath of about five to twenty lamellae. Small fibers 

 have no infoldings and fewer lamellae or none. Possibly there are systematic 

 differences in the surface area in relation to diameter, for Mr. Goldman in my 

 laboratory has consistently recorded a smaller, faster spike in the right 

 connective preceding the larger, slower spike identified by Dr. Tauc, while 

 he was with us, as that of the largest giant cell. The destination or distribution 

 of the giant fibers is not yet known except that the largest passes anteriorly 



Fig. 9. Large and small nerve fibers in a region of the fibrous core of the ganglion 



occupied by tracts more than by neuropile; there is a high content of glial processes 



here, in contrast to neuropile. Calibration: 100 micra. 



17 



