Volume 2

Health lectures for the people.

Date:
1883-1892
Catalogue details

Licence: Public Domain Mark

Credit: Health lectures for the people. Source: Wellcome Collection.

    216/600 (page 6)
    cient quantity of suitable food or fuel, and secondly, it must be suitably clothed. Had time permitted, it might perhaps have been interesting to have described the exact manner in which this fixed temperature is maintained under varying conditions. SuflSce it, however, to say that the heat-production is due to the chemical changes which are constantly taking place in all the tissues, more especially in the muscles, and great glandular organs such as the liver. That the heat-loss is in great part due to radiation and conduction from the surface of the skin, and to the evaporation of the surface moisture or sweat; and that the balance between the heat-production and heat-loss is regulated by a beautiful, self- adjusting or automatic nervous mechanism. When, for instance, the body is placed in a cold atmosphere (a) the vessels in the skin contract; less blood passes through the superficial or surface circulation; less heat is .consequently carried to the surface, for the blood is the great means or channel through which the heat, which is produced in the deeper tissues, is distributed through the body ; (&) the condition of the skin is so altered that its power of transmitting or conducting heat is diminished; (c) the secretion, and therefore the evaporation of sweat is greatly lessened. For all these reasons the heat-loss is very much diminished, and the body does not cool down and reach the temperature level of the surrounding atmosphere, as an inanimate object or even a cold blooded animal would do. But further, the temporary application of cold to the surface not only lessens the heat-loss, but it so acts upon the central nervous system that the heat-production is actually increased. In this way chiefly by the diminution of heat-loss, but partly by the increase of heat- production, the cooling of the body is prevented. Now in very cold climates nature requires to be assisted in her efforts at maintaining a fixed temxperature. The Laplanders, for instance, eat large quantities of blubber and fat which are eminently heat- producing foods, and clothe themselves with furs in order to form an additional non-conducting heat barrier between the severe external cold and their own warm bodies.