UNANESTHP:TIZED POIKILOTHERMIC DOG— KELLER 



67 



in figure 4 is an example of the former group and 557 also circled is an example 

 of the latter group. 



The differential lesions are schematized in the drawing in figure 5. When the 

 junctional tissue lying hetween the hypothalanuis and midbrain is coagulated, as 

 delimited by the stippled circle, without infringing materially upon the structural 

 integrity of the hypothalamic gray the animal is rendered poikilothermic without 

 any lowering in basal energy metabolism. This same result is attained by complete 

 transection of the brain stem at any level below the hypothalamic gray as indicated 

 by the straight line. But, when the heat-regulating nerve cells are ablated at the ex- 

 pense of consideral)le cephalic encroachment upon the structural integrity of the 

 tuberal and anterior hypothalamic gray as delimited by the S(jlid circle, a reduction 

 in basal energy metabolism results in addition to rendering the animal poikilo- 

 thermic. 



Analysis of these differential tissue defects and associated deficits forces the con- 

 clusions that physiological regulation against cold is primarily a neural affair, a 

 function of the neural hypothahiinus, whereas the normally elevated basal energy 

 metabolism is an endocrine affair, presumably a function of the endocrine hypo- 

 thalainiis. 



The possibility that the basal energy metaljolism deficit might be directly due to 

 "neighborhood" involvement of the adenohypophysis cannot be entirely ruled out. 

 However, it is doubtful that this is the case because these preparations exhibit no 

 other hypophysial deficits (except possibly sex atrophy) and further it is necessary 

 to remove the larger part of the adenohypophysis before a basal energy metabolism 



hypophysis 



Fig. S. — Diagram schematizing the differential lesions for separation of mechanism for regula- 

 tion against cold and the mechanism for reduction in basal energy metabolism. See text for 

 further reference. 



