836 PERIODIC FUNCTIONS IN MAMMALS 



adaptation, as long as no other secondary synchronizers, with a more 

 acceptable schedule, are given the chance to become dominant. Much 

 work remains to be done on the adaptability of the daily period, a 

 problem which also has been discussed by Kleitman (1949), Utterback 

 and Ludwig (1949). Behnke (1951) and Brindley (1954). Behnke 

 has justly emphasized the fact that efficiency loss and fatigue may 

 result when daily rhythms are desynchronized from the sleeping and 

 waking cycle. More recently, Lewis and Lobban (1957a,b) investi- 

 gated 24-hr rhythms in human subjects on long-maintained unusual 

 time routines in two isolated communities in Spitzbergen and, what 

 is of methodologic importance, they examined their data by a modified 

 form of Fourier analysis. While initial adaptation of excretory rhythms 

 in their subjects to a 21-hr routine or to a 27-hr routine was un- 

 common, such adaptation progressively improved, but was seldom 

 complete, even after six weeks on the new environmental routine. 

 Their subjects carried specially adjusted wrist watches showing 12 hr 

 during 10 1/2 ordinary hr (21-hr time) or showing 12 hr during 13 Vi 

 ordinary hours (27-hr time). The authors point out that these watches 

 were worn by the subjects to facilitate strict adherence to the ex- 

 perimental routine even when the subjects were away from base, an 

 aim which is hkely to have been achieved. On the other hand, the 

 question may be raised as to how easy it may have been for the 

 subjects to compute from one look at the clock (giving experimental 

 time) the corresponding "control" time (24-hr time, BST). If, as 

 would appear, easy arithmetic would have sufficed for the latter 

 purpose, the new time schedule according to which activities were 

 scheduled may have been "compared," occasionally, with time on a 

 24-hr day basis. The awareness of the corresponding old time (24-hr 

 time), in turn, even if it was subconscious [in the psychologist's 

 terminology: "suppressed" (out of experimental loyalty)], may have 

 conceivably counteracted the effect of activities on the experimental 

 schedule (either 21-hr time or 27-hr time), at least with respect to 

 the phase control of some of the rhythms studied. If this assumption 

 is correct, the degree to which one or the other excretory rhythm 

 adapted to the new routines could have depended upon the dominance 

 over phase control of one or the other time schedule. But whether or 

 not we are dealing in this case with interacting synchronizers, and 



