842 PERIODIC FUNCTIONS IN MAMMALS 



ciency (Flink and Halberg, 1952; Halberg and Visscher, 1953a). We 

 shall have to ascertain whether or not this effect of chronic thyroid 

 insufficiency is the result of associated adrenal cortical hypofunction. 



Let us now refocus upon the adrenal cortex as the "driver" of a 

 cellular sequence of events. Such driving could result from corticoid 

 effects (not necessarily direct ones) upon one or a few pacemaking 

 reactions. Corticoids may be pacemakers of 24-hr periodic metabolism 

 simply by changing certain conditions of the transport of reactants — 

 by effects exerted, e.g., upon permeability (Hechter, 1957; Szego, 

 1957). At any rate, in verified states of cortical adrenal insufficiency 

 ("generator" removal) certain 24-hr rhythms [but not all of them 

 (Hamilton et al., 1950; R. B. Howard, 1952)] are gravely altered. 

 Those in motor activity, rectal temperature, and feeding are damped 

 out, and only to these we may perhaps apply the analogy of damped 

 oscillatory circuits. It must be recognized that in the case of these 

 rhythms of the body as a whole, the neural control (and its exogenous 

 triggers, if present) is more direct, as compared with the corticoid 

 control via feedbacks, but the latter control also matters. Does the 

 corticoid effect concern the amplitude of these rhythms (of the body 

 as a whole) more prominently than their phase? The lack of strength 

 (for motor activity) and the lack of appetite, appearing early and 

 consistently in adrenal insufficiency, are both pertinent in this con- 

 nection, as is also the accompanying hypothermia. 



It must further be emphasized that the statistically ascertained evi- 

 dence involving the adrenal cortex as a control of certain 24-hr 

 rhythms differs from case to case. For the eosinophil rhythm of human 

 beings, the extinction of synchronized rhythm in verified cortical 

 insufficiency has been established (Halberg^/ a/., 1951) and confirmed 

 (Kaine et al., 1955) with sufficiently frequent serially dependent 

 sampHng. The eosinophil rhythm in the mouse has been established 

 by a variety of sampling procedures (Brown and Dougherty, 1956; 

 Halberg and Visscher, 1950, 1952; Halberg, Visscher, and Bittner, 

 1953; Louch et al., 1953; Panzenhagen and Speirs, 1953), but its 

 "obliteration" was examined only in serially independent data (Hal- 

 berg, Visscher, and Bittner, 1953; Brown and Dougherty, 1956). The 

 data on hepatic phospholipid metabolism in the mouse (Halberg, 

 Barnum, and Vermund, 1953; Halberg et al., 1956; Vermund et al., 



