i 



834 PERIODIC FUNCTIONS IN MAMMALS 



Visscher, and Bittner, 1953), but the feeding time can also govern the j| 

 phase of rhythm under certain conditions (idem.), and under other 

 conditions either noise or smell may do the same (Halberg, Visscher, 

 and Bittner, 1954). 



Thus a centrally situated area in the brain stem, functioning as a 

 unit, is subject to excitation by peripheral sensory input. Effects of 

 such excitation in turn lead to electrical activation of the cerebral 

 cortex and behavioral arousal of the animal (French et ah, 1952). 

 The status of our knowledge on the role played by the cerebral cortex 

 with respect to 24-hr periodicity has been discussed by Bykow, on the 

 basis of I. P. Pavlov's thesis ". . . that all (or we may say cautiously 

 almost all) reactions in animals, which can change as a function of ex- 

 perimental conditions, are brought about by temporary connections 

 established in the highest, phylogenetically youngest, and most per- 

 fected parts of the central nervous system" (Bykow, 1953). It is via 

 such connections that the cerebral cortex probably participates in the 

 control of phase of rhythms, but the added question arises whether the 

 cerebral cortex is essential for the occurrence of 24-hr periodicity. The 

 latter question, however, has tentatively been answered in the negative, 

 at least with respect to sleep and wakefulness (Kleitman, 1952). 

 Minnesota work on the same problem may be of interest, even though 

 it does not decide the question just raised. Thus, in hemiparetics with 

 epilepsy, the rhythms in rectal temperature and blood eosinophils per- 

 sist after the removal of one hemisphere, with or without certain of the 

 subcortical ganglia on one side, left or right (Halberg, French, and 

 Gully, 1958). In this case, however, we do not deal with the complete 

 removal of the cerebral cortex. In the same connection, let us allude 

 to the behavior of rhythms (Fleeson et al., 1957) during regression 

 induced by intensive electroshock therapy (R.E.S.T.) (Glueck et al., 

 1957). "Regression" represents a degree of dissociation from the en- 

 vironment seldom seen in humans. The patients are mute, disoriented 

 owing to complete memory loss, are doubly incontinent, and show 

 neurological changes associated with extrapyramidal tract activity. 

 Data on two paranoid and one catatonic schizophrenic female patients, 

 obtained in Minnesota (Fleeson et al., 1957) (before, during, and 

 after R.E.S.T.), reveal that the rhythms in eosinophils and tempera- 

 ture persist during the "regressed" state (induced by the daily adminis- 



