212 Heating and Cooling of the Body by Local Heat and Cold. 



from the skin or by rays which had penetrated the skin and had been con- 

 verted into heat in the blood, as pointed out by Sonne (3). He used thermo- 

 electric couples to determine the effect of different rays from the sun and 

 found that the visible rays penetrate the skin and locally heat up the blood. 

 To this he attributes the value of the sun in heliotherapy. Dark heat rays 

 heat up the surface of the skin much more. 



Summary. 



Experiments in which the hands were heated or cooled by water 

 showed that the amount of heating or cooling was large, but not constant, for 

 a given range of temperature. Some indication of the degree of heating or 

 cooling was obtained from the temperature of the skin over the median vein 

 at the elbow, the thermometer used being coiled and insulated from the air. 

 Loss of 20 to 25 kilo-calories of heat from the hands in 30 minutes, i.e., a loss 

 almost equal to the basal metabolism, did not appreciably affect the body 

 metabolism. 



EEFERENCES. 



(1) Hill, Leonard, ' Journ. Physiol.,' vol. 54, Proc. cxxxvii. 



(2) Macleod, Self, and Taylor, 'Lancet,' September 25, |1920, p. 645; Macleod and 



Taylor, ibid., July 9, 1921, p. 70. 



(3) Sonne, 'Acta Medica Scandinavica,' vol. 54, p. 394 (1921). 



