A text-book of human physiology / by Dr. Robert Tigerstedt ... tr. from the 3d German ed. and edited by John R. Murlin ... with an introduction to the English ed., by Professor Graham Lusk.

  • Robert Tigerstedt
Date:
1906
Catalogue details

Licence: Public Domain Mark

Credit: A text-book of human physiology / by Dr. Robert Tigerstedt ... tr. from the 3d German ed. and edited by John R. Murlin ... with an introduction to the English ed., by Professor Graham Lusk. Source: Wellcome Collection.

Provider: This material has been provided by the Augustus C. Long Health Sciences Library at Columbia University and Columbia University Libraries/Information Services, through the Medical Heritage Library. The original may be consulted at the the Augustus C. Long Health Sciences Library at Columbia University and Columbia University.

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    1. The above-mentioned destruction in a majority of cases is an oxidation, that is, a combustion of the substances called organic foodstuffs—proteid, fat and carbohydrate—at the disposal of the cell (Lavoisier, 17?7). This is proved by the fact that all animals produce carbon dioxide, and that they succumb in a short time in the absence of oxygen. Since a plant under the influence of sunlight has the power to reduce carbon dioxide and set oxygen free, it follows that under suitable circumstances plants and animals can live if they be kept together in a closed room; for the carbon dioxide formed by the animals is reduced by the plants with the liberation of oxygen; and thus each receives the gas most useful in its life processes. And yet we are not to suppose that the plant does not form any carbon dioxide. On the contrary the plant protoplasm in its production of kinetic energy behaves exactly like the animal protoplasm and produces carbon dioxide in the same way. The production of carbon dioxide in green plants in the light is masked by the much more abundant reduction of carbon dioxide going on at the same time; in the dark, however, where the reduction processes are checked, it is plainly perceptible. In the decomposition brought about by the vital activity the combustible substances are not broken down immediately into their end products; but the complex organic molecules are split up gradually into less and less complex ones, oxidation and reduction processes probably taking place in rapid suc- cession (Drechsel). Finally, these intermediate decomposition products are transformed into substances which leave the body as the end products of metabolism. 2. The living cell itself regulates the amount of oxygen consumed, combus- tion in the body being, within wide limits, entirely independent of the partial pressure of the uncombined oxygen (Pfliiger). In addition protoplasm has the power to store up oxygen in compounds in which it is loosely held, and from which it may be withdrawn again in case of need. This is witnessed by the fact that cells can develop kinetic energy, though in general only for a relatively short time, without a supply of free oxygen from outside. In certain cases this happens even at the expense of compounds which contain oxygen firmly bound up chemically and which cannot be deoxidized with our strongest reducing agents. We have examples of such phenomena in the Myxomycetes which continue their movements for three hours in an oxygen-free medium; in ciliated cells which can live still longer without oxygen; in the skeletal muscles which contract and give off carbon dioxide even in a vacuum. The mawworm, Ascaris, can live five days without a supply of oxygen (Bunge). In this case there occurs in the body of the animal a process of fermentation by which CO, and a mixture of valerianic acid, caproic acid, etc., are formed from the glycogen stored in the animal's tissues (Weinland). Here should be mentioned also the liberation of oxygen by hen's eggs during the first five hours of their incubation (Ilasselbalch). A very pretty experiment on the life of higher animals in the absence of oxygen is the following which we owe to Pfliiger. At 2.44 o'clock two frogs were placed in an atmos])here cooled to about 0° C. from which every trace of oxygen had been carefully removed. At three o'clock they showed the most pronounced dyspna?a but no convulsions. They soon became motionless, as if they wished by suppression of their movements to obviate the need for oxygen.
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