Investigations into the conditions governing the temperature of the bod}'. 17 



has become normal, perhaps subnormal; then we have the fall of 

 temperature. 



The relation of temperature to work has however two phases, 

 and in this case we obtain as good information from the negative 

 as from the positive. On sitting still the temperature is lower than 

 during exercise, in a quiet, reclining position still lower and during 

 sleep lowest Ч Sleep itself does not tell upon the temperature; the 

 fall of temperature is exclusively due to the fact that the organs 

 which produce heat have reduced their activity to a minimum. This 

 holds good especially for the work of the muscles, but of course it 

 ought to be taken into consideration that the other main factor in 

 the production of heat, the digestive function, is generally resting 

 just within the same period. The fall of temperature during sleep 

 is exceedingly variable; it is greatest when the sleep comes after an 

 active period, least when some hours have been passed in quiet 

 sedentary work previously. The morning temperature (temperature 

 on waking up) is however fairly constant under ordinary conditions 

 for the same individual; 72 morning measurements at different sea- 

 sons (all self observations) gave as average 3646° + 0"0013, p. = 

 014 or 038 "/0 of average. 



In 57 measurements taken twice, before and after sleep, in 4 

 different individuals, I have 47 times found negative deviations, 8 

 times positive and twice no difference, the average deviation being 

 —0-46". Of these 32 with average —0-45^^ fall in the "dark period", 

 25 with average — 049° in the light period of the year. On divi- 

 ding the cases into two groups according as the sleep took place 

 between 8 p. m. and 8 a. m. or between 8 a. m. and 8 p. m.. for 

 sleep in the night (30 cases) there is an average deviation of — 047° 

 and for sleep in the day (27 cases) of — 045°. For the summer, at 

 night (14 cases) the average was — 046°, in the day (11 cases) — 0-52°; 

 for the winter, at night (16 cases) the average was — 049°, in the 

 day (16 cases) — 0'41°; 14 cases of 1 — 3 hours sleep gave an average 

 deviation of — 054°. 



There is a tendency in these numbers which agrees with other 

 observations on sleep and strengthens the view, that the fall of 

 temperature is due to the fact that muscular activity during sleep 

 is at a minimum. It is well-known, that the first hours of sleep 

 are the soundest and quietest and the sleeper wakes with greater 

 difficulty than when the sleep has lasted for a longer period. The 

 quite short sleep of 1 — 3 hours shows, indeed, a greater fall of 

 temperature than all measurements taken on the whole, i. e. the fall 



1 Cf. Johansson's researclies in Skand. Archiv f. Ph. 7, 1891 

 XLIV, 1. 



