

NORMAL PEOCESSES OF ENERGY METABOLISM 603 



normal. Loewy(c) and Johansson conducted carefully controlled respira- 

 tion experiments by two different methods with a view to the determination 

 of the pure effect of cold. The former employed sixteen different subjects, 

 cooling the body not only by exposure to a temperature of 12 to 16 C., 

 but also by evaporation of water, alcohol and ether from theskin. The 

 latter performed experiments upon himself as subject after acquiring the 

 power to suppress all shivering or even increased tonus, when the naked 

 body was exposed to a room temperature of 13 to 20 C. Both observers 

 found that there was no increase in the elimination of carbon dioxid when 

 the muscular factor was really ruled out. Uncontrolled shivering in 

 Loewy's experiments produced an increase of 100 per cent in the metabo- 

 lism. 



Lefevre(d) has demonstrated that the loss of heat from the skin does 

 not follow Newton's law of cooling exactly because of certain physiological 

 adjustments of which the skin and subjacent structures are capable. 

 Nevertheless a better estimate of the influence of the environing tempera- 

 ture can be obtained by measuring the cooling power of the environment 

 on a surface at body temperature than is given by a record of the outside 

 temperature alone. The recognition of this truth led Leonard Hill (6) to 

 invent an instrument known as the "Kata-tbermometer." This consists of 

 a large-bulbed spirit thermometer which is warmed up until the meniscus 

 rises above 1 00 F. The rate of cooling is then determined with a stop-watch 

 as the meniscus falls from 100 F. to 95 F. The constants of the instru- 

 ment are determined, from which the cooling can be expressed in mille- 



calories ( grm. calories) per sq. cm. of surface per second. The 



instrument when used dry gives the rate of cooling by convection and radia- 

 tion and when used wet (covered with a damp muslin glove) gives the 

 rate of cooling by convection, radiation and evaporation. From the read- 

 ings of the dry instrument can be deduced the velocity of movement of the 

 dry air. The evaporative cooling power of the wet instrument depends 

 on absolute humidity and wind. 



Comparisons made by Hill between the rate of cooling of the Kata- 

 thermometer with that of the naked pig as determined by Lefevre and 

 of the naked surface of the human forearm as determined by Waller, and 

 with the dryness or sweating of the skin of soldiers producing a known 

 amount of heat, suggests that the Kata-thermometer in air cools about 

 three to five times as quickly as the naked skin when the temperature of the 

 skin approximates closely to the body temperature. 



Ordinary light clothes reduce the cooling power of the atmosphere 

 of a man as well as of the instrument to one-half its value when unclothed. 



The cooling power by radiation and convection exerted on the surface 

 of the dry Kata-thermometer at 36.5 C. in mille-calories per sq. cm. per 

 second according to Hill is as follows. 



