an overheated room. In such a room the blood vessels 

 ■pft f * °f the skin are dilated, the body tempera- 



~ . . ture rises, the pulse increases, the blood 



pressure falls. The brain and inner organs 

 are robbed of blood. One feels dull and listless and disin- 

 clined to exertion. The New York State Commission on 

 ventilation showed that when there was a powerful incentive 

 exertion was possible for short periods at high temperatures, 

 but that under ordinary conditions 6 per cent, more work 

 was done at 68° than at 75° and 15 per cent, more than at 

 86°. Prof. Ellsworth Huntington, from exhaustive studies 

 of the effect of season and climate upon physical and mental 

 work, finds a mean outdoor temperature of 60°-64° most 

 favorable for efficiency, summer and winter both showing a 

 marked falling off as compared with fall and spring. It 

 cannot be doubted that the excessive temperatures main- 

 tained in many factories (often combined with high humid- 

 ities, which accentuate the effect by checking evaporation 

 of perspiration) militate very seriously against industrial 

 efficiency. In military life the important influence of climate 

 upon bodily vigor should be borne constantly in mind in 

 the selection of training camps. 



The avoidance of gross overheating (temperatures above 

 v , f .. 68°) is not the only factor to be considered. 



M The body must be protected against the 



debilitating effect of heat on the one hand 

 and against the shock of excessive chilling on the other. 

 Within reasonable limits, however, variations in tempera- 

 ture, and particularly movement of the air, are important 

 factors in promoting health. The body owes its marvellous 

 power of maintaining its own temperature constant through 

 a wide range of outside temperatures to the reaction of the 

 skin blood vessels, which contract to keep the blood out of 

 the skin when it is cold and expand and bring the blood to 

 the surface when a more rapid heat loss is desired. The 

 tiny muscles in the walls of these blood vessels must be ex- 



18 



