MAINTENANCE OF THE BODY TEMPERATURE 373 



coast is declared to be more trying than the same season 

 inland although the thermometer goes much lower in the 

 interior. For the same reason that water feels colder 

 than air of the same temperature moist air feels colder 

 than dry. High humidity makes us warmer in summer 

 and colder in winter. 



In discussing the conditions affecting the metabolism 

 we have shown how the body meets external cold. The 

 skeletal muscles are called into extra activity. Without 

 special coverings to keep the heat pent in the body one 

 cannot be still. A rise in the metabolism is secured 

 which is, as we have insisted, essentially a case of exer- 

 cise. We have saved ourselves to a great extent from 

 the need of such an increase by adapting our clothing to 

 the weather. Animals do the same thing by posture. 

 On a hot summer day a cat may be found stretched at 

 full length with the tail extended and the paws well 

 apart. In this position the fur along the ventral surface 

 is opened to the air. 



On a cold day the cat squats with its paws pressed 

 against the body, the tail laid alongside, and the ventral 

 aspect covered in from the air. The surface exposure 

 cannot be one-half of what it is 'in the extended attitude. 

 Rabbits generally keep the squatting position and its 

 value is shown by the fact that they readily succumb to 

 cold when they are prevented from doing so. This is 

 the more striking because rabbits endure the most severe 

 climates. 



Temperature Regulation during Exercise. We have 

 considered thus far the problem of temperature main- 

 tenance with varying outward conditions. We have 

 found that within wide limits this is a matter of restrict- 

 ing or facilitating the loss of heat from the body rather 

 than a regulation of the rate of heat production. When 

 a man who has been resting rises and sets out on a brisk 

 walk we have a distinct case to analyze. External 

 factors may be unchanged but the metabolism is much 

 increased. If the body is to be successful in avoiding a 





