68 



PHYSIOLOGY OF INDUCED HYPOTHERMIA 



deficit is in evidence (see data in figure 4) . It is not a matter of the adenohypophysis 

 being dependent upon nerve impulses passing from the hypothalamus to the hypo- 

 physis through the infundibulum because the adenohypophysis can be completely 

 separated from the hypothalamus either by simple stalk section (Dog 295, figure 3) 

 or by a selective neurohypophysectomy'' without altering basal energy metabolism. 



It seems reasonably certain that this reduction in basal energy metabolism pre- 

 cipitated by associated massive involvement of the hypothalamic gray matter is the 

 underlying basis for (1) an increased sensitivity to anesthesia exhibited by these 

 preparations, (2) the decrease in the magnitude of a neurohypophysectomy poly- 

 dipsia,^*^ (3) the enhancement of pathological obesity when animals are maintained 

 on a fixed diet^^ and perhaps the permanent lowering of blood pressure both in the 

 normotensive and renal hypertensive dog,^^ as well as the increased threshold for 

 eosinopenic stimuli associated with hypothalamic lesions of various categories.^^ 



Temperature coefficient for heat production in poikilothermic dog. The 

 temperature coefficient for heat production in the completely poikilothermic dog 

 cannot as yet be stated with exactness, first, because of the small number of animals 

 studied and, second, because of the complication which a reduction in basal energy 

 metabolism introduces into the calculations. Heat production values at different body 

 temperatures are plotted in figure 6 opposite the cooling curves for 4 animals, 2 of 

 which were completely poikilothermic against cold and 2 which retained remnantal 

 non-shivering heat producing ability. 



45 



2.2 



CALORIES PER KILOGRAM OF DOG PER HOUR 

 2.0 L8 1 .6 1.4 12 LO 0.8 0.6 L4 0.2 



DOG 380 



T — I — I — I — I — r 



DOG 442 



1 — 1 — I — I — I — 1 — \ — \ — I I r 



DOG 350 



DOG 380 



45 

 44 

 43 

 42 



41 



38^ 

 37^ 

 36S 

 35- 

 34 J^ 



33 _, 



32^ 



31 [^ 

 -30'^ 

 - 29 



28 



27 



26 



25 



Fig. 6. — Cooling curves on left and heat production values for various body temperatures on 

 right for four dogs. Note that two were completely poikilothermic and two retained remnantal 

 non-shivering heat producing ability, as demonstrated by tlie cooling curves as well as the heat 

 production data. See text for further reference. 



