NERVOUS PATHWAYS 
regulation. However, a control of that sort by splanchnic nerves 
remains possible, but it is not yet thoroughly investigated. 
Thus the control of the musculature in its motor activity seems 
to bethechief nervous factor in chemical regulation in the dog, since 
the remaining thermogenetic power after extensive muscular de- 
nervation is poor. Moreover, the part of the hormonal control 
appears very small and restricted to the effects of epinephrine 
secretion, at least ifone lays aside the slow processes of adaptation. 
All of our preceding results are expressed as a correlation 
between thermal production and ambient temperature. Now, by 
varying ambient temperature we try to submit the animal to various 
thermal demands. One can ask whether the correlation is with am- 
bient temperature or with peripheral skin temperature. In the latter 
case, the value of our results must be questioned. 
Indeed, there is often in those animals a great reduction of the 
thermal sensitive skin area by nervous section. It is then necessary 
to know the significance of the measured calorification and of its 
maximum, and what kind of reaction is reflected by it. 
Besides the ambient temperature, two other values can be inves- 
tigated, the mean skin temperature and the difference between skin 
temperature and ambient temperature. This last value can provide 
information on the thermal gradient, and hence on heat loss. We 
made such an estimation on some of our animals which were para- 
lyzed or which lacked nervous section, by measuring three or four 
skin temperatures in the still sensitive area at different ambient 
temperatures in steady conditions. The calorific production, P, 
measured during a period of 20 minutes, is plotted against super- 
ficial temperature t , or t - t where t is ambient temperature. 
The difference between superficial and arnbient temperature (t - t ) 
appears to give a good correlation, while there is no correlation 
with t (Fig. 7). 
The deficit in thermoregulation of the dog with extensive mus- 
cular denervation remains unchanged for months. Besides, it 
becomes apparent only in severe cold. In mild cold exposure, heat 
production develops in a progressive and adapted manner. There is 
a limitation of but not a disorder in the regulation. 
237 
