EFFECT OF EXTERNAL TEMPERATURE 513 



The mouse was in the ventilated respiration chamber, surrounded by 

 a water-bath at 25, for fifty minutes before the first perio>l. The mouse 

 was fully under the anaesthetic when it was taken out of the respiration 

 chamber and recovered in about fifteen minutes. The periods are con- 

 secutive, and each determination of the output of carbon dioxide is for 

 fifteen minutes. 



The practical importance of the influence of anaesthetics upon 

 the regulation of temperature is now recognised by many surgeons. 

 An anaesthetised patient during and after a long operation should 

 be protected from exposure even to moderate cold, and his 

 temperature should be maintained by external sources of heat, 

 such as warm water-bottles. Drugs which produce profound an- 

 aesthesia can never be considered harmless : it is, indeed, probable 

 that the recovery of patients from the effects of operations is fre- 

 quently retarded or prevented by the depressing influence of the 

 anaesthetic, whereby the combustion of the body, one of the most 

 characteristic signs of life, has been so greatly diminished, and for 

 a time at least has been removed from the control of the nervous 

 system. Pain is a natural safeguard, and brings about appro- 

 priate responses to sensations which are too often quenched by 

 an anaesthetic. Animals and savages rapidly recover from serious 

 wounds or operations, although no drug is used to deaden the 

 pain, and civilised man does not succeed in abolishing pain even 

 during operations without paying a daily toll in human lives. 



The normal response of a warm-blooded animal to changes of 

 external temperature can also be abolished by curare or section 

 of the spinal cord, whereby the central control of the muscles is 

 removed. 



After the consideration of these abnormal conditions, which 

 demonstrate so clearly that the effect of external temperature 

 upon the respiratory exchange is bound up with the regulation of 



2 K 



