THE TEMPERATURE OF THE BODY 1173 



In the former animal, where the regulation of the temperature of the 

 body is effected almost entirely by changes in heat production, the effect 

 of warming the environment of the animal on the C0 2 output is extremely 

 marked. It will be noticed that the C0 2 per hour sinks continuously with 

 rising temperature up to 32 C. When the temperature of the chamber was 

 raised to 35 the temperature of the animal rose considerably, i.e. the 

 regulatory mechanism was failing, so that the same effect was produced on 

 metabolism as is observed in working with cold-blooded animals. The 



-0 



/o ao so 



Ext!r bemp, deg. CenC. 



w 



FIG. 545. Effect of variations in the external temperature on the C0 2 output 

 (per 1000 cm. 2 body surface) of warm-blooded animals. (C. J. MARTIN.) 



same change, though less marked, is observed on exposing the rabbit to a 

 gradual rising temperature. Here, however, the process of regulation is 

 aided by alterations in the heat lost as well as in the heat production (Fig. 

 545). If the animals be observed, whilst subjected to changes of tempera- 

 ture, it will be evident to any one that the regulation is associated with 

 changes in muscular activity. At 30 to 35 C. the animals will he perfectly 

 flaccid, breathing rapidly, or may go to sleep. On cooling they at once 

 become more vigorous and perform active movements in their cage. The 

 same effects of changes in the external temperature are familiar in our- 

 selves. The slackness and extreme disinclination to violent exercise ob- 

 served in hot moist weather, contrasted with the stringing up of the tone 

 of the muscles which follows exposure to cold, and which may be associated 



