INFL UENCE OF DA Y AND NIGHT. 



801 



The following curve 1 (Fig. 79) represents the mean results of records 

 of the temperature of the urine taken by Eichet, Gley, and Eondeau ; the 

 times of meals were 7 A.M., 11 A.M., and 7 P.M., and no observations were 

 made between 9 o'clock in the evening and 7 o'clock in the morning. 



Daily variations in 

 temperature, similar to 

 those already described, 

 have been observed in 

 natives of different 

 races living in the 

 tropics. 2 



As regards . the 

 causes of the daily 

 variation in tempera- 

 ture, muscular activity 

 and food appear to be 

 the most important 

 factors. In ordinary 

 life man is most active 

 and takes food during 

 the day, and is least 

 active during the night. 

 Debczynski 3 found that 

 continuous work carried on throughout the night reversed the variation, 

 so that the maximal temperature 37'8 occurred in the morning, and the 

 minimal 35'3 in the evening. Night-watching without work had a similar 

 but smaller effect, the maximal temperature 37'7 being in the morning, 

 the minimal 37'5 in the evening. Jaeger 4 has obtained similar results, 

 and Krieger 5 states that work during the night and rest during the day 

 reverse the daily variation. The influence of inversion of the ordinary 

 routine of daily life has been studied by U. Mosso 6 ; a series of observa- 

 tions of the rectal temperature was first made during a period when work 

 was performed in the daytime and sleep taken at night, and the two chief 

 meals were at 11 A.M. and 6 P.M. ; then there followed another period in 

 which sleep was taken during the day and work performed at night, and 



1 Richet, Rev. scient., Paris, 1885, tome ix. p. 430. 



2 Dav) T , "Researches," London, 1839, vol. i. p. 169 ; Jonsset, Arch, de med. nav., Paris, 

 1883, tome xl. p. 124 ; Maurel, Bull. Soc. d'anthrop. de Paris, 1884, tome vii. p. 381. 



3 Jahresb. ii. d. Leistung. . . . d. gcs. Med., Berlin, 1875, Bd. i. S. 248. 



4 Jaeger, Deutsches Arch. f. Idin. Med., Leipzig, 1881, Bd. xxix. S. 533. 



5 Ztschr.f. Biol., Miinchen, 1869, Bd. v. S. 479. 



6 Arch. ital. de biol., Turin, 1887, tome viii. p. 177. 



VOL. I. 51 



