232 DR SUTHERLAND SIMPSON ON 
above, although it may modify it to a considerable extent, cannot account entirely for 
this diurnal fluctuation. They believe that there exists in the body a fixed periodicity 
of which the temperature rhythm is an expression, and that this periodicity persists 
under all conditions, and is, to a large extent, independent of outside influences. Others 
are inclined to question the existence of this mysterious periodicity, and to look upon 
the diurnal variation as being due entirely to the action on the body of the influences 
already mentioned, which are known to raise or lower the temperature. 
II. Previous Work ON THE SUBJECT. 
If these factors are alone responsible for the diurnal temperature wave, then any 
modification in the application of them, and particularly any change in the time — 
within the twenty-four hour period at which one or more of them operate, might be 
expected to produce a corresponding change in the temperature curve, or, in the 
simplest and most complete case, total inversion of the daily routine should cause a _ 
complete inversion of the temperature curve. 
Various attempts have been made by different investigators to produce an inverted 
day-and-night curve, but these have been unsuccessful in the human subject. It is” 
true that the earlier observers, DeBczyNskI,* JAEGER,t and Bucuser,{ claim to have — 
succeeded, but when the conditions under which their experiments were carried out 
come to be examined, it is found that the methods of all three are open to criticism, 
and that their results are inconclusive. 3 
More recently Mosso § (1885) and Benepict || (1903), in carefully planned experiments, 
have studied the effect of night work and day rest and sleep on the temperature rhythm, — 
and both have arrived at the conclusion that the normal temperature curve cannot be 
inverted by inverting the daily routine, for while rest and sleep during the day lower 
the temperature, work during the night does not appreciably raise it. ‘The curve is” 
modified by the altered conditions but it is not reversed. 
‘hese results then would appear to show that the daily oscillations of the body 
temperature are not due directly to the causes already mentioned, but that they may 
have a deeper significance, and may indicate a diurnal periodicity in the body 
comparable in character to the seasonal and lunar changes that are known to ocet 
in certain plants and animals. That the temperature rhythm is to some extent fixed 
in the body is the most obvious interpretation to be put upon the failure of Mosso and 
BeENEDIcT to invert it, and this apparent fixity of rhythm is dithcult to explain. As 
Brnepicr says: “ Why the temperature of the human body reaches a minimum at 
* DeEBcZYNSKI, Abstract in Jahresb. der ges. Med., Bd. x., 1875, p. 248. 
+ Janaur, Deutsches Arch. f. klin. Med., Leipzig, Bd. xxix., 1881, p. 533. & 
{ Bucusmr, quoted by Carrur, Jour. Nerv. and Ment. Dis., vol. xvii., 1890, p. 785. 
§ Mosso, Archives italiennes de biol., vol. viii., 1887, p. 177. 
|| Benepicr, Amer. Jour. of Physiol., vol. xi., 1904, p. 143. 
