PERIODICITY IN HUMAN BEINGS AND MICE 



861 



In work with Professor E. Johnson (Division of Biostatistics, Uni- 

 versity of Minnesota), e.g., a potency ratio of 1 to 4 was obtained for 

 samples from the same batch of E. coli endotoxin (Difco) tested on 

 separate groups of comparable animals (for an LD-^o), when assays 

 were made 12 hr apart, at predicted times of low and high suscepti- 

 bility, respectively. It would be pharmacologically important if cer- 

 tain therapeutic-toxic ratios also change periodically. In such as yet 

 hypothetical cases, one may eventually revise some customary prac- 

 tices of drug administration (at clock hours chosen for convenience 

 only). 



Species Difference 



Figures 30, 31, and 33 summarize some of our knowledge on the 

 timing of 24-hr rhythms in human beings and mice. Important species 

 differences may first be seen for the rhythms in body temperature 



Mice 



Men 



12.45 



00.45 12.45 



TIME ( hours) 



00.45 



Fig. 31. Species difference in mode of synchronization of eosinophil 

 rhythm with environment. 



