HISTORICAL REVIEW 
ward. If these impulses were the efferent action potentials con- 
trolling shivering which arose in the fields of Forel, then destruction 
of the fields of Forel should abolish shivering. In a study of small 
lesions made bilaterally to destroy the fields of Forel, shivering 
persisted (Stuart, Freeman, and Hemingway, 1959). Another dis- 
turbing feature was that the duration of the spike potentials was not 
exactly the same asthedurationof shivering. The potentials seemed 
to persist after shivering had ceased. These observations reveal that 
any interpretation that the large well defined spike potentials of the 
midbrain which come and go with shivering form the efferent con- 
trol of shivering must be proposed with caution. Further research 
is needed. This work will be discussed by Dr. Freeman. 
ACKNOWLEDGMENTS 
The history of the search for an understanding of the neural 
control of the responses of the hypothalamus to cold has revealed 
that considerable progress has been made since the days of Isen- 
schmid in 1912-1914. In acknowledging useful contributions to this 
field of study, the workof Sherrington, Bard, Keller, Ranson, Clark, 
Magoun, Thauer, and Hensel has advanced our knowledge over that 
known in 1914. For the studies conducted at the University of 
California, which have been briefly reviewed in the latter part of 
this report, the Arctic Aeromedical Laboratory in Alaska has 
played a major role by encouragement, scientific liason, and finan- 
cial support. It is a pleasure to acknowledge their cooperation and 
to commend the staff, particularly Colonel Quashnock, Lt. Colonel 
Herbert, Drs. Hannon and Eagan, for their contributions to the field 
of environmental physiology by arranging this Symposium. 
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