466 ANIMAL PHYSIOLOGY. 
It is plain that vaso-motor changes alone can not explain 
these effects; and, though possibly a part of the rise of tem- 
perature, following exposure of the naked body in a cool air, 
may be accounted for by the increased metabolism of internal 
organs, accompanying the influx of blood caused by constric- 
tion of the cutaneous capillaries, it is probable that in this as 
in so many other instances the blood and circulation have been 
credited with too much, and the direct influence of the nervous 
system on nutrition and heat production overlooked or under- 
estimated. The thermogenic center has not yet been definitely 
located, though some recent investigations seem to favor a spot 
in or near the corpus striatum for certain mammals. Some in- 
vestigators also recognize a cortical heat-center. It has been | 
suggested that we may to advantage speak of a thermotowic 
(regulative of loss) and a thermogenic mechanism (regulative 
of production), and even a thermolytic or discharging mechan- 
ism. It has been further suggested that different nerve-fibers 
may be concerned in the actual work of conveying the different 
impulses of these respective mechanisms to the tissues; and the 
whole theory has been framed. in accordance with the prevalent 
conception of metabolism as consisting of anabolism and ca- 
tabolism, or constructive and destructive processes. But these 
theories have not yet been confirmed by experiments on ani- 
mals, though they are, in the opinion of their authors, in har- 
mony with the facts of fever. Certainly, any theory that will 
imply that vital processes are more under the control of the 
nervous system than has hitherto been taught, will, we think, 
advance physiology, as will shortly appear from our own dis- 
cussion of the influence of the nervous system on the various 
metabolic processes generally. 
The phenomena observable in an animal gradually freezing 
to death point strongly to the direct influence of the nervous 
system on the production as well as the regulation of heat. 
The circulation must of course be largely concerned, but it ap- 
pears as though the nervous system refused to act when the 
temperature falls below a certain point. A low temperature 
favors hibernation, in which we believe the nervous system 
plays the chief part, though the temperature in itself is not the 
determining cause, as we have ourselves proved. The fact that 
the whole metabolism of a hibernating animal is lowered, that 
with this there is loss of consciousness much more profound 
that in ordinary sleep, of itself seems to indicate that the nerv- 
ous system is at the bottom of the whole matter. 
