KAWAMURA, Y. 
proprioceptive input is more prevalent in these experiments in the 
limbs on which the animal is lying than in the freely suspended 
tongue, jaw, and neck muscles. When inducing shivering by electrical 
stimulation of the central nervous system, Stuart and Kawamura 
have found shivering easier to induce in the limb muscles; but in 
these experiments the animals' heads were held in a stereotaxic 
frame. 
Reerulatory Considerations 
Perkins (1945) has suggested that the rhythm of shivering is 
controlled by proprioception but instigated and maintained by central 
hypothalamic activity. Such a concept followed his recording a 
change in the frequency-amplitude characteristics of hind limb shiv- 
ering following deafferation. The most characteristic EMG pattern 
of a shivering muscle is a grouping voltage occurring 10-12 times 
per second, the same frequency as the hind limb oscillations re- 
corded by Perkins. When we cut the dorsal roots the grouping 
voltages became randomized and shivering lost its characteristic 
rhythm. This finding is a confirmation of Perkins* original findings. 
However, as mentioned earlier it is suggested that proprioceptive 
input as well as regulating the rhythm of shivering also facilitates 
its initial occurrence. 
SUMMARY 
Following electromyographic analysis, the muscles of dogs at 
various stages of shivering intensity, rectaltemperature, and anes- 
thetic level, the following conclusions appear in order: 
1. The order of appearance of shivering in muscles is (a) jaw and 
tongue, (b) neck, (c) hind limb, (d) forelimb, with extensor 
muscle shivering more intense and appearing earlier than flexor 
muscle shivering. 
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