KAWAMURA, Y. 
shivering continued for four to five hours and in the waning stages of 
anesthesia was again concurrent with lung inflation. The duration 
of grouped discharges shortened thus reflecting a lesser number of 
NMU discharges fusing into the group discharge. Intervals between 
each elongated grouped discharge lengthened and at this stage visible 
limb movements ceased (Fig. 6). 
Differences Between Muscles During Shivering 
Grouped discharges and NMU discharges were observed in jaw, 
tongue, andneck muscles before limb and trunk muscles and as shiv- 
ering waned it disappeared earlier from jaw muscles than from 
others. The above pattern was not evident when the head or limbs 
were restrained by being tied to a board which usually resulted in 
inhibition of the specifically restrained body part. 
Muscles of the hind limb had a tendency to become active earlier 
than the fore limb. Extensor muscle groups became active before 
flexor muscle groups, agonist and antagonist discharges being con- 
current rather than reciprocal; there was one grouped discharge 
from any one muscle fiber per one full limb cycle (Fig. 7). Addition- 
ally there were a greater number of NMU discharges fused into the 
grouped extensor discharges than NMU discharges fused into grouped 
flexor discharges. 
Jaw muscle shivering and electrical activity was most predom- 
inant in the horizontal position of the lower jaw. 
The Relation of Shivering to the Level of Anesthesia 
Under deep anesthesia (light mydriasis - corneal reflex absent) 
none of the animals shivered. Three of the 10 animals shivered con- 
comitant with lung inflation when a weak corneal reflex was evident. 
At this level of anesthesia shivering was induced in the other 7 
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