CHAPTER XXXIX 



METABOLISM UNDER VARYING CONDITIONS 



THE body requires a certain amount of energy for the performance 

 of its functions during rest. This is known as the basal requirement, 

 and is best ascertained by determining the respiratory exchange of 

 a person in a state of complete rest twelve hours after the last 

 meal, which should not have been rich in carbohydrate. Such a 

 state is best obtained in bed, before rising, in the early morning, 

 when the surrounding medium is uniform in temperature, the muscles 

 are well rested, and other systems of the body, such as the alimentary 

 system, are more or less inactive. 



15* 



-rW~-P4v 



-+ 



: H 4. 



I I I 

 1 I I 



H3U 



- f {-_.. 



._^4-J 



FIG. 190. DIAGRAM TO ILLUSTRATE THE RELATION BETWEEN VOLUME OR WEIGHT 

 AND SURFACE. (Waller.) 



The volumes are 1, 8, 27 c.cm. ; the weights are 1, 8, 27 grammes; the surfaces are 

 6, 24, 54 square cm.; the ratio of increase is 1, 4, 9. 



Of this basal requirement it is calculated that 10 to 20 per cent, 

 of the total energy is required for the maintenance of the work of 

 circulation and respiration. 



The Weight of the Body and the Surface Area. The larger the 

 nmss of an animal, the greater its absolute energy requirements, and 

 the greater its absolute consumption of material. While this is true 

 for the absolute, it is not true for the relative amounts. The 

 smaller the animal, the relatively greater is its energy output. This 

 is because, calculated per kilo body weight, small warm-blooded 

 animals have a proportionately greater surface area. They have 

 therefore need of a greater heat production, involving an increased 

 metabolism. 



341 



