PERIODICITY IN HUMAN BEINGS AND MICE 839 



(neurally?) a "comparison" must be made between the composite 

 phase information from within the body and that from without, 

 COPI and CEPI, respectively. The composite organismic phase 

 information (COPI) may be yielded by the mixing, weighting, and 

 combining of information from various feedbacks, psychogenic, neuro- 

 genic, hormonal, and metabolic. The composite environmental phase 

 information (CEPI), in turn, may schematically be subdivided into 

 the potentials evoked by the sync signals of the physicochemical 

 environment (EPI;,) (light being an important case in point), and 

 into those evoked by other signals, arbitrarily designated as "socio- 

 ecological" (EPI J cf. Aschoff, 1958). Most likely, EPI„ our social 

 schedule (and our "emotional" response to it) is more critical in 

 determining the phase of bodily rhythms in urbanized human beings, 

 while EPIp might be more pertinent for humans living in the setting of 

 an isolated farm. But to separate experimentally the effects of EPI,, and 

 EPL constitutes no minor undertaking in the case of man. This same 

 task seems more amenable to study in certain experimental animals, 

 even though in the latter EPE also has dramatic and often unexpected 

 effects. We may only allude to studies carried out, inter alios, by 

 Gangloff and Monier (1956) on the unanesthetized rabbit. The 

 electroencephalographic changes occurring in this animal, when it is 

 confronted with the investigator, probably involve "emotional" com- 

 ponents, and these thoroughly studied changes (Gangloff and Monier, 

 1956) are actually more striking than the corresponding changes 

 evoked by light in itself. Moreover, such "emotional" EPIs, interfering 

 with EPIp, involves not only brain waves, with their short periods, but 

 also the 24-hr rhythm in rectal temperature and even the daily 

 sequence of periodic cellular events, such as mitosis (Halberg, in 

 press). Unless we anticipate these varied effects, their contribution 

 via EPIs to CEPI will remain uncontrolled. It becomes evident that 

 in studying the effect of a change in EPIp (e.g., in the lighting 

 schedule), we must endeavor to evaluate, for experimental animals, 

 as well as for human beings, possible concomitant changes in EPI.,. 

 It can hardly be overemphasized that ambiguous results obtained in 

 studies of effects of EPI,, can quite easily be brought about by our 

 failure to evaluate inadvertent yet critical changes in EPI.v. At any 

 rate, changes either in EPIp or in EPL (or in both) can alter CEPI. 



