Rudiments of animal physiology : for use in schools, and for private instruction / by G. Hamilton.

  • Hamilton, George, 1808-1885
Date:
1839
Catalogue details

Licence: Public Domain Mark

Credit: Rudiments of animal physiology : for use in schools, and for private instruction / by G. Hamilton. Source: Wellcome Collection.

Provider: This material has been provided by the Francis A. Countway Library of Medicine, through the Medical Heritage Library. The original may be consulted at the Francis A. Countway Library of Medicine, Harvard Medical School.

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    death would undoubtedly take place ; but if no carbonic acid were formed, we shall find that the heat of our bodies could probably not be maintained. When charcoal is burned in atmospheric air, the changes which occur seem to be almost precisely similar to those that are produced by respiration. Ox3^gen disappears, and carbonic acid is formed. It seems rea- sonable, therefore, to conclude, that the heat produced in both cases is connected with these changes. That the production of animal heat bears some resemblance to combustion, is rendered probable by the following considerations:—1st, It has been determined by experiment that the charcoal contained in the carbonic acid formed during a given period by respiration, would give out, when burned, fully more than half the heat produced by the animal in that period. It takes no less than about eleven ounces of carbon to form the carbonic acid of an ordinary man's daily respiration. Dr Milne Edwards thinks that this, and the superabundant oxygen which is absorbed by the blood (which probably combines in great part with hydro- gen to form water), will account for nine-tenths of the heat an animal produces, the remaining tenth probably being the pro- duct of the friction of the different parts of the body, the changes occurring in secretion, &c. 2dly, This view is sup- ported by the fact, that the temperature, in the different classes of animals, very accurately corresponds to the quantity of oxygen consumed. The temperature of birds is highest, and they consume most. The young, among the Mammalia, con- sume the least, and have the temperature lowest. Indeed, it may be remarked, that the young of most of the Mammalia, including children, have much difficulty in supporting any great degree of cold wh«n separated from their parents; and where incautious exposure takes place, the mortality among them is found to be very great. Reptiles, which consume little oxygen, have a temperature only a few degrees above the medium in which they live ; and the same may be said of fishes, w^ith the remarkable exception of the Cetacea (whale, porpoise, &c.), which have a high temperature, but consume much oxygen, as they breathe air by lungs. 87. It has been thought, however, that as the carbonic acid is given off in respiration, and the oxygen disappears at the same time, the temperature of the lungs ought to be much higher than that of other parts, and it was to meet this diffi- culty that Dr Crawford proposed his celebrated Theory of Ani- 7nal Heat. He maintained that the capacity for heat (as che- mists call it) is greater in arterial than in venous blood ;' that * What is meant by capacity may be rendered intelligible thus :— If we mix one pound of water at the temperature of 60 degrees, with
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