. A text-book of comparative physiology [microform] : for students and practitioners of comparative (veterinary) medicine. Physiology, Comparative; Veterinary physiology; Physiologie comparée; Physiologie vétérinaire. THB METABOLISM OF TUB BODT. 451 to understand how by the law of habit and heredity each group of animals has come to prefer and flourish best upon a oertain diet. But habit itself implies an original deviation some time, in which is involved, again, plasticity of nature and power to adapt as well as to organize. Without this, evolution of func- tion is incomprehensible ; but with
. A text-book of comparative physiology [microform] : for students and practitioners of comparative (veterinary) medicine. Physiology, Comparative; Veterinary physiology; Physiologie comparée; Physiologie vétérinaire. THB METABOLISM OF TUB BODT. 451 to understand how by the law of habit and heredity each group of animals has come to prefer and flourish best upon a oertain diet. But habit itself implies an original deviation some time, in which is involved, again, plasticity of nature and power to adapt as well as to organize. Without this, evolution of func- tion is incomprehensible ; but with this principle, and the tendency for what has once been done to be easier of repetition, and, finally, to become organized, a flood of light is thrown upon the subject of diet, digestion, and metabolism generally. On these principles it is possible to uudei-stand those race differ- ences, even individual differences, which as facts must be patent to all observers. The principle of natural selection has clearly played a great part in determining the diet of a species; the surviving immi- grants to a new district must be those that can adapt to the local environment best, including the food which the region supplies. The greater capability of resisting hunger and thirst in some individuals of a species implies great differences in the meta- bolic processes, though these are mostly unknown to us; and the same remark applies to heat and cold It seems clear that hibernation is an acquired habit of the whole metabolism, with-great changes in the functional condi- tion of the nervous system recurring periodically, and, in fact, dependent on these, by which oertain large divisions, as the reptiles, amphibians, and certain mammals among vertebrates, are enabled to escape individual death and extinction as groups. We may suppose that, for example, among invertebrates, by a process of natural selection, those survived that could thus adapt themselves to the environment; while, among m
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Keywords: ., bookauthormillswes, bookcentury1800, bookdecade1890, bookyear1890
