THE MAINTENANCE OF THE BODY TEMPERATURE 201 



the reduction in the volume of blood in the cutaneous 

 vessels. It is the expression of the endeavor of the organ- 

 ism to economize to the utmost its outgo of heat. Dis- 

 comfort is permitted to develop as an incident of the adap- 

 tation. The metabolism still remains about as it has been 

 throughout the series of trials. 



If the room temperature is now lowered decidedly and 

 no wraps are provided the body can no longer maintain 

 itself by mere economy of heat loss. It must shift from 

 the method of the incubator with a constant flame and 

 an adjustable ventilator to the other form of regulation 

 that of the thermostat with variable flame. That is to 

 say, the metabolism must be stimulated. A sign of this 

 rallying on the part of the heat-producing tissues is seen 

 in the onset of shivering. This is obviously a form of 

 muscular exercise, and as such is attended with increase of 

 metabolism. When we resist the impulse to shiver, as 

 we sometimes do, we merely adopt another kind of con- 

 tractile activity with its accompanying contribution of heat 

 to the body. If we analyze the experience of being cold 

 we find that we can recognize a disposition to muscular 

 tenseness, while it is familiar enough that when the cold 

 is severe we cannot keep from moving briskly and so sup- 

 plying the necessary heat. It is desirable to reiterate that 

 the muscles are not merely organs of movement, but our 

 main reliance for heat production. Cold weather generally 

 means large metabolism, but the connection is indirect; the 

 increase is only a special case of the rise always associated 

 with exercise. So, too, the increase of appetite which is usual 

 in winter is secondary to the greater use of the muscles. 



Humidity makes for discomfort in cold as well as in 

 warm weather. It seems at first unreasonable to say that 

 moisture can make us more sensitive to heat in summer 

 and also to cold in winter, yet this is true. The climate of 

 our Atlantic coast is notorious for the "penetrating" char- 

 acter of its cold, and this in spite of the fact that the 

 thermometer does not fall so low as it does a short distance 

 inland. The paradox is easily explained. We have said 



