THE NEURAL CONTROL OF THE 
PHYSIOLOGICAL RESPONSES TO COLD 
HISTORICAL REVIEW 
Allan Hemingway 
Professor of Physiology 
University of California School of Medici 
Los Angeles 24, California 
In the animal kingdom, only birds and mammals have the abil- 
ity to maintain rectal temperature within a narrow range in spite 
of wide changes of environmental temperature. This property of 
homeothermy is not possessed by the lower vertebrates or any of 
the invertebrates. The homeotherms have physiological responses 
to cold and warmth under control of the central nervous system 
which are absent in the poikilotherms. 
In analyzing the physiological responses to cold and heat 
which the homeotherms possess, the following physiological mechan- 
isms are observed: For protection against heat, the homeotherms 
can (1) dilate their cutaneous vessels and raise their skin tempera- 
ture to facilitate heat loss and (2) increase evaporative cooling by 
sweating or panting. For protection against cold, the homeotherms 
can increase their metabolic heat by (1) shivering and (2) nonshiv- 
ering thermogenesis and can (3) reduce heat loss to the environ- 
ment by cutaneous vasoconstriction. The control of body tempera- 
tures by cutaneous vasoconstriction and vasodilation is a physio- 
logical mechanism functiong continuously throughout the day and 
throughout life. It is this mechanism which maintains rectal 
temperature nearly constant in a comfortable environment. Shiv- 
ering, panting, and sweating are emergency functions which only 
become active during cold or heat stress. 
This system of physiological mechanisms which functions to 
maintain homeothermy is under the control of the central nervous 
system which functions with remarkable efficiency as a thermo- 
stat to activate, inhibit, and regulate the component functional 
physiological processes of homeothermy. A survey will now be 
given of the experimental data which in recent years has served to 
establish our current concepts of how the central nervous system 
functions to protect against cold. 
