818 



PERIODIC FUNCTIONS IN MAMMALS 



sively, from without) from the chain of gear wheels as it is actuated 

 by springs and weights (maintenance, critically, but not exclusively, 

 from within). 



We have much to learn about those factors concerned with the 

 maintenance of rhythms, and it seems likely that nervous, endocrine, 

 and metabolic interactions are involved. At the time of this writing, 

 however, the role of the adrenals, at least, seems established as a 

 critical factor in the maintenance of several 24-hr periodicities in the 

 mammal, even though many of the pertinent data represent merely 

 spot checks; the nature of the variables involved often limits the fre- 

 quency of sampling. Thus, for the following considerations, time series 

 of sufficient length for the numerical estimation of the period or the 

 amplitude, e.g., by periodograms, are not available. In viewing Fig. 

 12, we are dealing only with the day-night differences in certain 24-hr 



I 



300 



E 

 E 



CELL 

 (BLOOD) 



200 





« 



'■B 100 

 o. 

 o 

 _c 

 'in 

 o 



IB 



Adrenals 

 removed 



No 



il LIGHT 



mi DARKNESS 



10 -r 



17 





y 8 



c 

 O 



to 



S2 



NUCLEUS 

 (EPIDERMIS) 



15 



40 



<30 

 to 



i^ 



24 



rr!m a. 



o 





I20 



Q. 



o 10 

 a. 



Yes 



No 



Yes 



CYTOPLASM 

 (LIVER) 



m 



23 



\S223< 









22 



No 



Yes 



Fig. 12. Effects of adrenalectomy upon blood eosinophils, epidermal 

 mitoses, and hepatic phospholipid metabolism in the mouse. 



periodic variables, selected from several levels of physiologic organiza- 

 tion. This figure reveals, however, that such differences are significant 

 in the presence of the adrenals, but are not statistically significant after 

 removal of the adrenals (Halberg, Barnum, and Vermund, 1953; 



