66 



PHYSIOLOGY OF INDUCED HYPOTHERMIA 



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5 9 13 17 19 



45 UNOPERATED DOGS. 



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Fig. 4. — Basal heat production values as calculated from measured oxygen consumption. 

 To the left, designated by solid circles, are the individual values for 45 unoperated dogs. In the 

 center are individual values for Z6 animals after large hypothalamic ablations, designated by 

 crosses. To the right are values for 6 litter mates before and after varying degrees of adeno- 

 hypophysectomy ; a pituitary stalk section designated by crosses, partial hypophysectomies 

 designated by open triangles and solid stjuares and near-total hypophysectomies by solid circles, 

 open s<|uares and open circles. 



13-17 kg. weight range 1.70 CaUn-ies and for the 17-19 kg. weight range 1.65 

 Calories. 



The hypothalamic coagulations reduced basal heat production materially in all 

 l)ut 5 dogs (5-8) and in four instances to the level of 1 Calorie per kg. per hour 

 which is in the neigh])orhood of a 40 per cent reduction and is equal to the maximal 

 lowering which follows an appropriate adenohypophysectomy. Encountering a 

 graded reduction in basal heat production in a group of dogs which also exhibit a 

 graded impairment in ability to regulate against cold at first sight might cause one to 

 suspect that these deficits are directly related ; particularly because of the assump- 

 tion so widely expressed in the literature that endogenous epinephrine and thyroxin 

 are utilized to increase non-shivering heat production during cold exposure. Quite to 

 the contrary, the two deficits seem not to be related, because dogs can be rendered 

 completely poikilothermic against cold without anv associated decrease in basal 

 energy metabolism. .Mso, an animal which stilTers a ma.ximal reduction in ])asal 

 heat may retain considerable cold-combatting po\sers. Dog 447 circled in the chart 



