[Cytochemical index of the function of the afferent fiber]

A correlation between the spike activity and ferrous deposits in the Ranvier nodes of afferent fibers has been revealed in the frog bladder. The degenerated fibers reveal neither deposits, nor spike activity. The native fibers reveal deposits in the presence of spike activity. When the spike activity is suppressed by procainamide the node affinity to ferrous ions is retained. It is suggested that positive cytochemical reactions in the nodes demonstrate the retention of the initial morpho-functional structure of afferent fibers.