PERIODICITY IN HUMAN BEINGS AND MICE 863 



and blood eosinophils (Figs. 30, 31). Whether we compare the tim- 

 ing of the ascending phases of rhythms or that of the descending 

 phases, the phase difference between the two species is prominent for 

 either rhythm. 



With respect to the temperature graph (Fig. 30), it is pertinent 

 that orally obtained data are shown for man (Halberg et al, 1951), 

 while rectal temperatures are graphed for mice (Halberg, Levy, and 

 Visscher, 1953). This limitation, while real, may contribute only 

 slightly to the species difference in timing, since both temperatures 

 (oral and rectal) approximate the behavior of the core of the body 

 rather than that of its periphery. It is recognized, of course, that very 

 significant differences in the timing of temperature rhythm may be 

 had in the same individual, if, for instance, temperatures are recorded 

 from the mouth and an extremity (Fig. 32). 



In Fig. 33 epidermal mitotic counts on mouse pinna are compared 

 with counts made by the late Dr. Zola Cooper (1939) on prepuces 

 removed at circumcisions carried out at various times of day. The 

 comparison cannot be justified by the similarity of absolute counts in 



6 



W I- 



<rt -O r- 



o — D 



♦- Q. 



.- a, 



o 



I 



_L 



Mouse 



/ \ Man 



± 



± 



± 



08.45 



16:45 00:45 



Time of Day 



08:45 



Fig. 33. Species difference in mode of synchronization of epidermal 

 mitotic rhythm with environment. 



