The elements of the science of nutrition / by Graham Lusk.

  • Lusk, Graham, 1866-1932.
Date:
1909
Catalogue details

Licence: Public Domain Mark

Credit: The elements of the science of nutrition / by 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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    metabolism and that the metabolism was not proportiofial to the oxygen supply. The oxygen absorption apparently de- pended upon what metabolized in the cells. Voit believed that the cause of metabolism was unknown, that the process was one of cleavage of the food molecules into simpler pro- ducts, which could then unite with oxygen. Yeast cells, for example, convert sugar into carbonic acid and alcohol with- out the intervention of oxygen. In like manner the first pro- ducts of the decomposition of fat, sugar and protein, are formed in metabolism through unknown causes. Some of these preliminary decomposition substances may unite with oxygen to form carbon dioxid and water, others may be converted into urea, while others under given circumstances may be syn- thesized to higher compounds. In any case the absorption of oxygen does not cause metabolism, but rather the amount of the metabolism determines the amount of oxygen to be absorbed. (See P- 3I-) The statement is frequently met with in the literature of the subject that such and such a disease is the consequence of de- ficient oxidative power in the tissues. For example, it has recently been stated that alcohol decreases the oxidative power of the liver for uric acid.^ Such apparent decrease in oxidative power may, however, be due to the fact that the normal oxidiz- able cleavage products are not formed and therefore no oxida- tion can take place. It is not due to lack of oxygen that sugar is not oxidized in diabetes, or cystin in cystinuria. There is the normal supply of oxygen present, but the cleavage of these substances into bodies which can unite with oxygen cannot be effected, and hence they cannot be metabolized. Voit's pupil, Lossen,^ showed that the carbon dioxid elimina- tion in respiration was independent of the ventilation of the lungs except in so far as forced breathing increased the muscular work and the consequent output of carbon dioxid. ^Beebe, S. P.: American Journal of Physiology, 1904, vol. xii, p. 36. ^Lessen: Zeitschrift fiir Biologic, 1S66, Bd. ii, p. 244; and 1870, Bd. vi, p. 298.