CHATONNET, J. 
capacities of dogs whose spinal cords are severed at thoracic one 
level (Fig. 1). In 10 to 12 dogs operated on in this manner, bilateral 
section of the brachial plexus induced an obvious disturbance of the 
regulation, very similar to those resulting from cervical lesions; 
below 0° C, the regulation failed and the central temperature de- 
creased when the cold exposure continued. Under the same conditions 
the heat production could not surpass a given level; we obtained a 
true maximum. 
Therefore, the muscular activity in the narrow field controlled 
by the cervical and brachial plexuses is able to provide an important 
though unmeasured part of the regulatory thermogenesis (Figs. 2 
and 3). Also, one can suppose that the regulatory power remaining 
after that operation depends on the activity of musculature in the 
neck and face, which is almost impossible to eliminate. 
Many other results point out the importance of the muscular 
factor in the heat production elicited by cold exposure . Hammel and 
Harcfy (1960) observed a very close parallelism between the bursts 
of shivering and the curve of heat production in the dog. During the 
intervals between these bursts the metabolism drops down to basal 
values. Carlson (1955) made similar observations in the rabbit. 
The old experiments on curarization are liable to objections 
because of the non-specific actions of drugs. Davis (1955), using 
curare, assigns the extra-motor reactions for 40 per cent of the heat 
production by the mouse in the cold. Werner and others (1956) found 
spontaneous rewarming of curarized dogs with blankets after anes- 
thesia in a room at 24 C, but the role of basal combustion is not 
taken into account. Cottle and Carlson (1954) noted a distinct in- 
crease of heat production of curarized rats exposed to cold, chiefly 
in adapted animals. 
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