332 



SLEEP-WAKEFULNESS CYCLE 



comprised sleep, lounging, duty, regular 

 meals, snacks, drinking of coffee or tea, and 

 such recreational activities as reading, writ- 

 ing, and playing of games. The writer was 

 assisted in this hourly survey by the pharma- 



Fig. 1. Parts I-IV show mean percentages of 

 officers and men in each of the four sections awake 

 during every hour. Data are based on nine full 

 24-hour periods. Bottom curve is a composite of 

 curves I, II, and III. 



cist's mate and the yeoman, each of the three 

 operating with one section, on a "4 hours 

 on and 8 hours off" schedule. The hourly 

 note-taking required about one-half hour of 

 the observer's time, which allowed short 

 intervals of rest between rounds. Unless on 



watch or asleep, each man was questioned 

 as to his activities during the preceding 

 hour and his intentions for the immediate 

 future. Nine individuals volunteered to 

 take their mouth temperature at 4-hourly 

 intervals during the cruise. This permitted 

 the correlation of the sleep- wakefulness cycle 

 with the diurnal body temperature curve. 



Routine of Living on U.S.S. 

 Dogfish under Way 



Sleep and Wakefulness 



As the men were allowed to sleep when 

 off duty, there was not a single hour during 

 which someone was not asleep. However, 

 the distribution of waking hours, plotted 

 in Fig. 1, is definitely skewed, even if the 

 plotting be based only on the three sections 

 who stood watches. In Section I (watches 

 4-8 and 16-20) between and 3 o'clock 

 only 13 percent of the men were awake, 

 while in the corresponding 12 to 15 o'clock 

 period over 50 percent were up. The same 

 was true of Section II (watches 8-12 and 

 20-24), were the percentages of men awake 

 between 4 and 7 and between 16 and 19 

 o'clock were, respectively, 6 and 53. Sec- 

 tion III (watches 0-4 and 12-16) largely 

 slept through the breakfast hour, but would 

 get up in time for dinner. Comparing the 

 two-hour periods between 8 and 10 and 20 

 and 22 o'clock, only 10 percent were awake 

 during the former, while fully 61 percent 

 staj'^ed up after supper. Section IV, which 

 did not stand watches, shows a single wave 

 of wakefulness during the 24-hour period, 

 with a low during the conventional sleeping 

 hours at night. The composite curve of the 

 wakefulness of the three watch sections, 

 which should theoretically give a horizontal 

 line at the 62 percent level (as their average 

 wakefulness comprised 14.9 hours per day) 

 resembles, instead, the curve for Section 

 IV. The diurnal range of wakefulness was 

 naturally greater for Section IV (93 to 21 

 percent) than for the other sections com- 

 bined (90 to 36 percent), but the maxima 

 were close and both occurred between 19 



