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

  • Graham Lusk
Date:
1917
Catalogue details

Licence: In copyright

Credit: The elements of the science of nutrition / by Graham Lusk. Source: Wellcome Collection.

    153/850 (page 153)
    However, on a liberal diet the metabolism increases on a damp day even at a medium temperature, as for example: Temperature 20.2° Calories in Humidity in 24 Hours Per Cent. Very dry day 249.4 13 Humid day 261.9 66 More on humid day 12.5 The increase is 5 per cent. On a very hot day (on a moderate fat diet) the dog’s metabolism is increased by the presence of moisture in the atmosphere. Temperature 35° Calories per Kg. Humidity in Per Cent. 69.28 9.1 73-54 30-° Under these circumstances the metabolism rose 6.1 per cent, in the more humid air. There was probably an overwarming of the cells on account of the difficulty of heat loss by evaporation of water. A cold, damp environment of o° to 50 temperature also favors an increased metabolism. Rubner attributes this action of humidity to the increased conductivity of a hair covering containing moisture, and says that this loss may be partially balanced by a decreased evaporation of water from the lungs. Murschhauser and Hidding1 have experimented with guinea-pigs placed in various environmental temperatures and furnished either with perfectly dry air or air completely saturated with moisture. At 350 the well-known influence of air saturated with water increased the body temperature and, therefore, the metabolism. At both 20° and 50 the influence of cold was accentuated by excessive dryness of the air, so that the heat production was about 10 per cent, higher than in moist air at the same temperature. This is explained by the fact that in dry air evaporation of water from the lungs increased the loss of heat by the animal which was compensated for by an increased metabolism. The metabolism and the manner of heat loss may, therefore, be variously affected by the condition of the atmosphere as regards moisture. On days of ordinary dryness Rubner2 calculates the following division of the heat loss in a starving dog under the influence of different temperatures: 1 Murschhauser, H., and Hidding, H.: Biochem. Z., 1912, 42, 357- 2 Rubner, M.: “Energiegesetze,” 1902, p. 193.