. A text-book of comparative physiology [microform] : for students and practitioners of comparative (veterinary) medicine. Physiology, Comparative; Veterinary physiology; Physiologie comparée; Physiologie vétérinaire. w. 448 COMPARATIVK PUTSIOLCKIY. The production of heat, however, wemi to be equally under the influence of the nervous â yitem, though we know lew about the detaila of the matter. A oold-blooded animal diffen from i^ warm-blooded one in that its temperature varies more with the lurrounding medium! hence the terms poUrilothermer and homoiothermer for cold* blooded and warm-bloo
. A text-book of comparative physiology [microform] : for students and practitioners of comparative (veterinary) medicine. Physiology, Comparative; Veterinary physiology; Physiologie comparée; Physiologie vétérinaire. w. 448 COMPARATIVK PUTSIOLCKIY. The production of heat, however, wemi to be equally under the influence of the nervous â yitem, though we know lew about the detaila of the matter. A oold-blooded animal diffen from i^ warm-blooded one in that its temperature varies more with the lurrounding medium! hence the terms poUrilothermer and homoiothermer for cold* blooded and warm-blooded, would be appropriate. Sueh an animal, as a frog or turtle, may have its chemical processes slowed or quickened, almost like Uiose going on in a test-tube or crucible, by altering the temperature. Very differ- ent is it, as we have seen, in the normal state of the animal with any mammal. Hence hibernation or an allied state has be- come a necessary protection for poikilothermers, otherwise (he; would perish outright, and the groups become extinct in * em latitudes. It is pill X 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 systeqi 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 ta or near the corpus striatum for certain mammals. Some in- vestigators also reoogniae a cortical heatoenter. It has been suggested that we may to advantage speak of a thermotaxie (rf>gulative of loss) and a thermogmtie mechan
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