PERIODICITY IN HUMAN BEINGS AND MICE 



815 



200 



Fig. 



06:oo 1 8:00 06:oo is.oo 



Time (hours) 

 10. Circadian activity periods after blinding in two stocks of mice. 



constant darkness is relatively independent of environmental tempera- 

 ture (Fig. 11) (cf. Pittendrigh, 1954). If, then, under several condi- 

 tions we see different bodily rhythms dissociating themselves from the 

 local time scale, we may remember that thereby ( 1 ) the rhythm itself 

 is not lost, (2) "physiologic time" is still being kept by periodic func- 

 tions, and (3) it is simply a new (average) period which has come to 

 the fore. This has been ascertained after blinding for the rhythms in 

 temperature, blood eosinophils, and body activity of mice, and can 

 also be suggested on the basis of spot checks for the rhythm in pinnal 

 mitoses. In our rectal temperature data, the free-running circadian 

 period is slightly but clearly shorter than 24 hr, a circumstance that 

 accounts for the differences in phase of rhythm between blinded mice 

 and sham-operated mice and this period can be measured as may be 

 seen in Fig. 4, which exhibits periodograms describing the behavior 

 of mean temperatures after blinding. It is apparent that, on the aver- 

 age, during the first month after operation we deal with a shortening of 



