THE TEMPERATURE OF THE MONKEY AND ITS DIURNAL VARIATION. 101 



system, and of the temperature-controlling system. The effect of muscular exercise on 

 the body temperature is well known. JtJRGENSEN (29) found that sawing wood for six 

 hours raised the rectal temperature of a healthy man l - 2° C. In one of ourselves a 

 sharp walk of an hour and a quarter on a cold frosty night caused an elevation of the 

 temperature of the rectum of l'V C. Obernier (30), Ogle (31), Crombie (32), and many 

 others have found the same. Quite recently Blake and Larrabee (33) have studied 

 the effect of severe muscular exercise on forty-five long-distance runners ; the course was 

 twenty-four miles. The temperature was taken by the mouth at the start, and by the 

 mouth and rectum at the finish. Very often the mouth temperature was lower at the 

 finish than at the start, but the rectal temperature was invariably higher, except in three 

 cases, where the runners had taken considerable quantities of alcohol during the race. 

 The highest rectal temperature reached was 40 '2° C, and this by three separate in- 

 dividuals. Unfortunately the rectal temperature was not taken immediately before 

 the start, but supposing it to be normal — 37'2 — the elevation would be 3° C. One of 

 the important facts demonstrated by these observations is that the mouth temperature 



I is not a reliable factor, especially after active exercise. By relying on the mouth 

 temperature, Marcet (34) and Lortet (35) were led into the error of supposing that 

 mountain climbing lowers the temperature. Benedict (6) found that the body 

 temperature was sensitive to even the minor muscular movements implied in changing 

 the position of the body. 



In animals the same effect has been observed. Richet (36) tied up a dog and 

 placed a very delicate thermometer in its rectum, graduated in 50ths of a degree. As 

 a rule, if the dog remained immobile the temperature did not vary and might remain 

 for some hours almost fixed ; but if the dog struggled or was excited for even ^ minute, 

 the temperature rose, 2, 3, or it might be 5, oOths of a degree, and after the temperature 

 had risen 5/50° C. it took about ten minutes to return to what it was before the move- 

 ment was made. Also by causing pigeons to fly with a weight attached to them, he 

 found that the temperature was raised from 1° to 2° C. in a few minutes. Mott (37) 

 lias noticed a rise of 1° to 2° C. in the temperature of monkeys after a short chase, and 

 we have observed a similar rise under the same conditions. 



With regard to the effect of sleep there is not the same unanimity of opinion. 

 According to Barensprung (38) and Wunderlich (39), sleep has no effect on the 

 temperature, but on the other hand Crombie (40), Hunter (41), Liebermeister (42), 

 land many others have found that during sleep the temperature always falls. In the 

 'experiments of Mosso (7) and of Benedict (6), sleep during the day caused a very 

 distinct fall, and seemed to be the most important factor in modifying the curve. 



Muscular exercise appears therefore to be the chief cause of an elevation of the body 

 I temperature, and this becomes most effective in those animals in which the temperature 

 [regulating mechanism is least highly developed; in monkeys it is more effective than 

 in man. Sleep, on the other hand, or a depressed condition of the heat-reculatin^ 

 centres (the central nervous system), is probably the chief cause of a fall in the 



