UM, T. P. K. 
In the experiments in which head and trunk temperatures were 
independently regulated, head temperature was controlled by warm- 
ing or cooling the carotid arterial blood. This was accomplished 
by inserting a glass coil in the course of arterial blood and then the 
glass coils were immersed in the water bath (Fig. 1). Figure 2 shows 
the glass coils (length = 1,5 m, i.d. =4 mm, o. d. = 6 mm): the 
proximal end of a caret id artery is connected to the inlet B and blood 
temperature is monitored by the thermocouple D. The three-way 
stopcock E served as a tap throu^ which air bubbles or clots may 
be removed. The temperature oi warmed or cooled arterial blood 
is recorded by the thermocouple C and the blood returns to the head 
of the animal through the outlet A which was cannulated to the distal 
end of a common carotid artery. 
In the study of thermal panting, the temperature of the animal's 
trunk was controlled by heating or cooling the trunk alone in a tem- 
perature cabinet which had heating and cooling units. On the other 
hand, in the studies of shivering, the regional cooling or warming of 
the trunk was accomplished by means of ice or warm water con- 
tained in a plastic sheet which covered the animals from the neck 
down to the thigh and extremities. 
The onset of thermal panting was defined arbitrarily when the 
respiratory rate reached lOO/min. To define the initiation of shiv- 
ering, the electromyogram was monitored from four muscle groups 
at the regionsof neck, thigh, lower, and upper legs. For this purpose 
the Gilson's electromyograph and integrator were used. The tracing 
A in Figures indicates the muscle potentials for 10- second duration. 
When any one of the afore- mentioned muscles begins to show a 
deflection of 3 mm (i.e., 6 to 9 mV in terms of the integrated po- 
tential) it is designated as the onset of shivering. 
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