PERIODICITY IN HUMAN BEINGS AND MICE 



831 



< 



^ - 3 



>- m 



< . p 



3 



a) Successive days 



Mean ' !IZ] }t I S.E. 



/Day no. I 2 3 



600 



< -> 500 



>; T 400 - 

 300 - 

 200 - 



3 



bj Successive 3-hour periods 



interrupted for 

 collections of urine 



1 5:00 21:00 03:00 09:00 



TIME (hours) 



15:00 



Fig. 16. Variation in urinary 5-hydroxyindoleacetic acid excretion in a 

 medically normal human male. In this case, variability along the 24-hr 

 scale seems to be larger than that from day to day. 



< o 



24:oo 



06;oo 12:00 



TIME (hours) 



18:00 



24:00 



Fig. 17. Periodicity of 5-hydroxyindoleacetic acid excretion in medically 

 normal students. 



