814 



PERIODIC FUNCTIONS IN MAMMALS 



7 8 9 10 



DAYS AFTER OPERATION 



Fig. 9. Circadian activity periods of two blinded mice compared with 

 activity of a sham-operated mouse. 



mice (Halberg, 1954b, Halberg and Visscher, 1953b, 1954a,b) 

 (Fig. 3). 



For the mouse. Fig. 8 reveals data on the eosinophil rhythm, and 

 Figs. 9 and 10 on the rhythm in gross motor body activity, measured 

 according to Bruss et al. (1958). It may be suggested that a variety of 

 mammalian functions can "free-run," and that their circadian periods 

 may underlie the dissociation of activity rhythm from the environment, 

 revealed already by some of the earlier work of Johnson (1939), Cal- 

 houn (1945), Aschoff (1951), Nothdurft (1951), and Browman 

 (1952) (for review see Aschoff, 1958). With respect to the activity 

 rhythm in the mouse, it is interesting (1) that blinding and the 

 maintenance in continuous darkness have similar effects, (2) that mice 

 born anophthalmic also may exhibit circadian periods (Fig. 5), and 

 (3) that the free-running period of activity rhythm of mice kept in 



