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exhibits the increased response due to the action of Na₂CO₃ on Pt. Another record shows an exactly similar effect on tin. The record of effect was taken two minutes after the application. Other records taken immediately after, show that the enhanced responsiveness takes place gradually with time.

Depressants.—Reagents, like KBr (10 per cent.), produce a depression in the response. There are again others which abolish the response almost completely, for example, 3 per cent. KHO solution (fig. 82, c). One of the most effective reagents which abolishes the response is oxalic acid. The depressing effect of this reagent is so great that a strength of 1 part in 10,000 is often sufficient to produce an abolition of response.^[1]

Fig. 82. Records showing the opposite effects of weak and strong solutions. (a) Normal response; (b) increased response due to addition of 0.3 per cent. KHO; (c) abolition of response by 3 per cent. KHO.

1. The various phenomena connected with the response in inorganic substances—the negative variation—the relation between stimulus and response—the increased response after continuous stimulation—the abnormal response converted into normal after long-continued stimulation—the diphasic variation—the increase of response by stimulants, decrease by depressors, and abolition by "poisons," so-called—all these are curiously like the various response phenomena in living tissues. A complete account of the mutual relation between the two classes of phenomena will be found in my work "The Response in the Living and Non-living."