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frog’s heart deformed ventricular systoles are generated, whereas it 
never brings about fibrillation of the ventricle. This finds an expla- 
nation in the fact that after digitalis poisoning (in a toxic dosis *)) 
the refractory stage of the ventricle is lengthened instead of shortened. 
Conductivity is then bad, however, so that a single deformed ventri- 
cular systole can arise, but the “Hrregung” cannot pass through 
the ventricle a second time. 
1) When speaking of digitalis-poisoning in a toxic dosis, 1 mean a dosage that 
lengthens the refractory stage and retards conductivity. 
