epithelium of amphibian embryos ( cynops orientalis , xenopus laevis ) was found in preceding experiments to generate and conduct impulses during a limited stage ( 26-37 ) of development . in order to elucidate the structural basis of impulse propagation , epithelial cells of four stages were examined by the freeze-etching method : ( i ) before and ( ii ) during acquisition of conductivity ;
C0678723
development
C0035150
propagation