832 



PERIODIC FUNCTIONS IN MAMMALS 



rectal temperature (Ferguson et al., 1957) of mice. These rhythms 

 were altered by hypophysectomy, but were not obliterated thereby. 

 The most prominent effect of hypophysectomy was a decrease in 

 amplitude of rhythm (Fig. 18; cf. also Miiller and Giersberg, 1957). 

 Moreover, periodograms revealed circadian periods, the dispersion of 

 which among individual animals was significantly greater in the 

 hypophysectomized group than in a group of intact mice studied con- 

 comitantly (P < 0.05; analyzed by Professor E. Johnson). A reduc- 

 tion in degree of synchronization of rhythms among individual mice 

 thus came to the fore at one month after hypophysectomy. Moreover, 



102- 



%\00 



98o 



12:00 



20 00 



Time of Day 



04;00 



Fig. 18. Decrease in amplitude of temperature rhythm, about one 

 month after hypophysectomy (r = 4 days; A/ = 4 hr). Mouse. 



evidence for desynchronization between the rectal temperature rhythm 

 and the lighting regimen was obtained at 5 months after hypophysec- 

 tomy (Ferguson et al., 1957). It seems interesting that at 5 months 

 after blinding, stimuli other than those received by the eye had gained 

 some control of the timing of rhythms that were desynchronized (free- 

 running) at earlier time points after removal of the eyes. At a com- 

 parable interval after hypophysectomy and in the presence of the eyes, 

 desynchronization of temperature rhythm and lighting regimen appar- 

 ently occurs. Some role of the pituitary in synchronization may thus be 

 unmasked, but this pituitary effect is probably indirect, since it must 

 be based upon observations made late after the operation when secon- 



