ANIMAL HEAT. 391 



should have been produced was 4124 calories. During the experi- 

 ment the calorimeter actually absorbed 3958 calories, a difference 

 between the theoretic and experimental results of 156 calories. 



Calorimetric experiments on man corresponding to those made 

 by Rubner on dogs have not been successful, owing purely to tech- 

 nical difficulties. Various attempts have been made, however, to 

 determine the daily heat-dissipation. Liebermeister immersed a 

 man in a bath with a temperature lower than that of the man's body. 

 From the rise in temperature of the water it was calculated that the 

 man produced daily 3525 calories. Leyden placed the leg alone of 

 a man in a calorimeter. In one hour 6 calories were absorbed. 

 Assuming that the total superficial area of the body was fifteen times 

 that of the leg, he calculated, taking into consideration various 

 sources of error, that the entire body would produce daily 2376 cal- 

 ories. Ott, employing a water calorimeter, found that the body of a 

 man produced 103 calories during an afternoon, or at the rate of 

 2472 calories daily. These and similar experiments, while not free 

 from many objections, furnish resujfe which_jndicate that the heat 

 dissipated from the body approximates the physiologic heat values 

 of the foods. 



HEAT-DISSIPATION AND REGULATION OF THE TEMPERATURE. 



Heat-dissipation. From the preceding statements it is evident 

 that the body is continually evolving heat in amounts daily far in 

 excess of that necessary for the maintenance of the. body-temperature. 

 ^Should this heat be retained, the temperature of the body would be 

 raised at the end of twenty-four hours an additional 18 or 20 C.,-^a 

 a temperature far in excess of that compatible with the maintenance 

 of physiologic processes. That the body may be kept at the mean 

 temperature of 37.8 C. it is essential that the heat evolved be dissi- 

 pated as fast as produced. This is accomplished in several ways: 



(1) In warming the food and drink to the temperature of the body. 



(2) In warming the inspired air to the same temperature. (3) In 

 the evaporation of water from the lungs. (4) In evaporating water 

 from the skin. (5) In radiation and conduction from the skin. 

 The quantities of heat lost to the body by these different processes 

 it is difficult for obvious reasons to accurately determine, and the 

 estimates usually given must be regarded only as approximative. 



Assuming 2500 calories to be an average amount of heat liberated 

 during a day of repose, the losses, in the ways stated above, may be 

 given as follows : 



i. In Warming Food and Drink. The average temperature of food 

 and drink is about 12 C.; the amount of both together is about 

 3 kilograms; the specific heat of food about 0.8. The absorption 



