ANIMAL HEAT AND FORCE 401 



Fahr. (about 5 1 to 57 C.), there was a continual craving for a strong, 

 animal diet, particularly fatty substances. 



The influence of alcoholic beverages on the animal temperature has 

 been studied chiefly with reference to the question of their use in en- 

 abling the system to resist excessive cold. The testimony of scientific 

 Arctic explorers is that the use of alcohol does not enable men to endure 

 a very low temperature for any considerable length of time. 



As a rule, when the respiratory activity is physiologically increased 

 as it is by exercise, bodily or mental, ingestion of food or diminished 

 external temperature the production of heat in the body is increased 

 correspondingly ; and on the other hand, it is diminished by conditions 

 that physiologically decrease the absorption of oxygen and the exhala- 

 tion of carbon dioxide. The relations of animal heat to the general 

 process of nutrition are most intimate. Any condition that increases 

 the activity of nutrition and of katabolism, or even anything that in- 

 creases katabolism alone, increases the production of heat. The reverse 

 of this proposition is also true. 



Notwithstanding the fact that there is a certain correspondence 

 between the activity of the respiratory processes and the production of 

 heat, this is far from absolute. It has been shown by Senator that 

 digestion increases heat-production rathej: more than it increases the 

 exhalation of carbon dioxide. Muscular work has been found to increase 

 the quantity of oxygen consumed in much greater proportion than it 

 increased the heat-production (Hirn). Even adding to the heat produced 

 the work, reduced to heat-units, the heat-production was about doubled, 

 while the quantity of oxygen consumed was increased about four and 

 a half times. 



Influence of Exercise etc., on the Heat of the Body. The most nearly 

 complete repose of the muscular system is observed during sleep, when 

 hardly any of the muscles are brought into action except those concerned 

 in tranquil respiration. There is always a notable diminution in the gen- 

 eral temperature at this time. In the variations in the heat of the body, 

 the minimum is always during the night ; and this is not entirely de- 

 pendent on sleep, for a depression in temperature is always observed 

 at that time, even when sleep is avoided. It is a matter of common 

 observation that one of the most efficient means of resisting the depress- 

 ing influence of cold is to exercise the muscles constantly ; and it is well 

 known that after long exposure to intense cold, the tendency to sleep, 

 which becomes almost irresistible, if yielded to, is followed by a rapid 

 loss of heat and almost certain death. Muscular work increases the 

 production of heat ; but the variations in the actual temperature of the 

 body in man, although distinct, are seldom considerable, for the reason 



