1316 PHYSIOLOGY 



THE NERVOUS MECHANISM FOR HEAT REGULATION 



The accurate balance between heat production and heat loss 

 which is responsible for the nearly constant temperature of man, 

 indicates the active co-operation of the central nervous system 

 in every step of the process. Whether this function of tempera- 

 ture regulation can be specially localised at any part of the 

 central nervous system, so that it would be possible to speak of a 

 heat-centre in the same way as we speak of a respiratory or vaso- 

 motor centre, is doubtful. Many observers have found that injury 

 to the corpus striatum causes a rise of temperature associated with 

 increase both in heat production and in heat loss. On the other 

 hand, injury to or pathological lesions of the pons Varolii often 

 lead to an increased production of heat in the body, which is not 

 compensated for sufficiently by heat loss, and so causes death by 

 hyperpyrexia. It has been suggested that the thermogenic centre, 

 i.e. that responsible for regulating heat production, is situated at a 

 lower level in the nervous system than the thermotaxic system, i.e. that 

 which presides over and determines the balance between heat pro- 

 duction and heat loss. The centres for heat loss must be placed 

 in the medulla, at any rate so far as concerns control of heat loss by 

 alterations in the blood-supply to the skin or in the secretion of sweat. 

 The facts at our disposal are, however, too meagre to warrant any 

 definite localisation of the heat-regulating function in the central 

 nervous system, or any such accurate analysis of the regulating 

 function as has been just suggested. 



In many warm-blooded animals the ability to maintain a con- 

 stant temperature is not fully developed until some time after birth. 

 Pembrey has shown that in the guinea-pig and chick, in which the 

 nervous system is fully functional at birth, the heat-regulating 

 mechanism is also completely adequate, whereas animals such as rats, 

 pigeons, or the human child, which are born in a helpless condition, only 

 acquire the power of regulating their own temperature some time after 

 birth. As we should expect, the development of the power of regu- 

 lating heat production runs pari passu with the acquisition of control 

 by the nervous system over the muscles of the body. 



