172 Maiiilciunax Riilioiis (iiul Sturrlt J'Jtjiiiraltntu 



with this hiw is necessary for t lie iiiaintcnance of a constant temperature. 

 \\'la-n Kubner first estaljiishcd tliis "law of surface area" he explained 

 its constancy on the assuinj)tion tliat the loss of heat from a liody 

 must depend uj)on tlie extent of tlie surface, and stimuli received from 

 that surface determined the amount of metabolism and so maintained 

 the body temperature while allowing for loss of heat by radiation. 

 But at a temperature of 30° C. where all possibility of thermal stimuli 

 was removed, Kubner found in the case of two guinea-pigs of different 

 sizes that the law still held, and the explanation that the variation 

 in metabolism of different animals was due to the "chemical regulation" 

 brought about by specific sensory influences of cold proceeding from a 

 definite area of surface, broke down. The insufficiency of the explana- 

 tion was realised by Kubner who, however, stated that even at this 

 temperature the law is still a necessity if the general mechanism for 

 loss of heat in the various animals is the same in all. From a jjhysio- 

 logical standpoint, it is difficult to accept this explanation. The meta- 

 bolism of a body must depend upon the mass of living cells it contains, 

 and the temperature of this nuiss, and the mecjianism for the regulation 

 of heat loss and the maintenance of a constant temperature, must 

 therefore be a subsidiary one, and not the determining factor of 

 metabolism. 



Each living cell must possess a basic recjuirement of energy at a 

 given temperature for its needs, and the heat produced as a result 

 of its activity must be a secondary result. The chemical regulation 

 consequently is only required when the heat so produced is insufficient 

 to provide for loss by radiation, etc., and maintenance of the cell at 

 its normal temperature. That this is so is supported by the fact that 

 where the food given is more than sufficient to supply the energy 

 requirements of the body, chemical regulation is not brought into play 

 until the temperature of the surroundings has fallen to the point 

 where the energy requirements supj)lied by the food are insufficient 

 to satisfy the body's requirements. Moreover, the path of heat loss 

 varies considerably according to the temperature of the environment. 

 Thus, whereas in a dog at low temperature the path of the heat loss 

 is through radiation by the skin, at a temperature of 37° C. the path 

 is by means of evaporation of the water from the lungs, and is 

 here independent of the surface. 



The normal energy metabolism of an organism as measured by 

 the heat loss consequently covers two things, (1) the basic energy 

 requirement of the living cell for the adequate expression of its activity, 



