860 



PERIODIC FUNCTIONS IN MAMMALS 



groups of comparable animals, exposed under comparable conditions 

 to one or the other noxious agent, predictably show maximal damage 

 from one agent at one time and from the other agent at another. 



By the use of such applied periodicity analysis the experimental 

 pathologist may then work at defined peaks or troughs in suscepti- 

 bility to a given agent. In pathology, certain more vulnerable parts 

 of the body have been described as spots of diminished resistance 

 (loci minoris resistentiae) . These spots now have their temporal 

 counterpart, the hours of diminished resistance (horae minoris re- 

 sistentiae or horae variae resistentiae, since one may wish to empha- 

 size the change in resistance, rather than its drop). In terms of experi- 

 mental documentation, the "hours" may not compare unfavorably 

 with the "spots." Information on a spectrum of peaks and troughs in 

 susceptibility seems useful as well to bioassayists interested in ap- 

 proaches to their sources of variations, particularly in regard to the 

 vexing problem of interassay variability. 



Mice ( 



no - 



rectal) 



Men (oral) 



c 

 ra 

 fit 



E 



" 105 



o S 



>^ LU 



O •- 100 



z >. 



< Q 



3: O 



U CO 



> 



< 



-J 



LU 



95 



- 101 



90 



100 



99 



12:45 00:45 12:45 00:45 



Fig. 30. Species difference in mode of synchronization of temperature 

 rhythm with environment. 



