Many systems can display a very short, rapid change stage (quasi-discontinu
ous region) inside a relatively very long and slow change process. A quanti
tative definition for the "quasi-discontinuity" in these systems has been i
ntroduced. With the aid of a simplified model, some extraordinary Feigenbau
m constants have been found inside the period-doubling cascades, the relati
onship between the values of the extraordinary Feigenbaum constants and the
quasi-discontinuity of the system has also been reported. The phenomenon h
as been observed in Pikovsky circuit and Rose-Hindmash model.