ANYONE who gives electric shock treatments is bound to have observed that the convulsion threshold rises successively during a series of treatments and then seems gradually to become stable. Some weeks after the final treatment the convulsion threshold is found to have resumed its original level. Kalinowsky1 refers to this phenomenon, which had been observed by Elsberg and Stookey2 before the introduction of electric shock therapy. Bárány and Stein-Jensen3 found the same tendency in animals. Toman and Goodman,4 in their experiments with animals, carefully studied the inhibitory period during some hours immediately after the electroconvulsions. As I had observed that the duration and intensity of the convulsive seizure appeared to decrease, while the convulsive threshold was increased during series of shock treatments, I thought it worth while to study these effects more closely. METHOD AND MATERIAL First, the duration of the convulsions was calculated for a