40 J- Lindhard. 



Daily variation of temperature. 



The problem occupying foremost place in thermometry within 

 recent times is the question whether the variation of temperature 

 during 24 hours follow a fixed, inherited curve invariable in each 

 individual; whether the curve of variation, as Finsen ^ puts it, "be- 

 longs to the mysterious land of periodicity", or is a simple conse- 

 quence of other physiological functions, the range |of which we may 

 consciously control and limit. Most authors have made the latter 

 view dependent on its being possible to find a "reversed" curve of 

 temperature on changing one's mode of life, by working at night 

 and sleeping during the day. For several reasons these experiments, 

 at any rate when made on human beings, must necessarily fail of 

 success, and the problem is still regarded as unsolved, though many 

 researches go to show that the л'ariations of temperature can be 

 explained from known presuppositions. 



The classical work in this field is Jürgensen's on the tempera- 

 ture of the body^. I shall not enter upon the general considerations 

 and theories advanced by Jürgensen, which seem to me too artifi- 

 cial, but restrict myself to his curves of variation. His "normal 

 curve" has by all later authors been adopted as the standard for 

 the daily change of temperature, and it cannot be denied that his 

 material was large and that his curves agree well with one another, 

 but nevertheless I think that his mode of procedure is open to 

 objection and his results deceptive. Firstly, he concludes from the 

 regularity displayed by his curves that the same regularity would 

 be found again under other conditions, even if disturbed by various 

 circumstances. He does not take into account the possibility that 

 the same persons, when living under quite different conditions, might 

 display as regular variations, but with curves of quite a different 

 shape and on another level. Secondly, he considers individuals 

 passing day and night in bed as normal individuals. He attains 

 what he is seeking for, regularity in the variations of temperature; 

 but he does not contribute towards the explanation of the phenomena. 



In Sweden important papers on the variations of temperature 

 have been published. 



By means of a long series of experiments on metabolic changes, 

 TiGERSTEDT and Sonden-^ have determined the amount of carbonic 

 acid given off during the 24 hours; they have compared the varia- 

 tions in the production of carbonic acid with Jürgensen's curve of 



1 Hospitalstidende 1894, No. 50, p. 1247. 



- Die Körperwärme des gesunden Menschen. Leipzig 1873. 



^ Skandinav. Archiv f. Physiologie G, 1895. 



