396 VARIATIONS IN THE MEAN BODILY TEMPERATURE. 



Cold thus stimulates muscular activity, which is attended with oxidation- 

 processes. In human beings muscular activity induces, in addition to increased 

 heat-production, also increased heat-dissipation. The latter, however, becomes 

 less on conclusion of the activity than it had been before. After administration 

 of curare, which paralyzes the voluntary muscles, this regulation of temperature 

 falls to a minimum. 



Strychnin increases heat-dissipation and heat-production, and the bodily tem- 

 perature may be either increased or diminished in accordance with the prepon- 

 derance of production (convulsions) or of dissipation. Cocain increases the bodily 

 temperature, while the anesthetics have the reverse effect. 



4. Change in the surrounding temperature has an influence upon the 

 need, for food. Ingestion of food increases the elimination of carbon 

 dioxid, principally in consequence of increased activity on the part of 

 the digestive glands. In winter, as well as in cold regions, the sense 

 of hunger and the need for fats, whose combustion yields much heat, 

 are increased. 



Regulatory Mechanisms Governing Heat-dissipation. 



The average dissipation of heat from the skin of a human being 

 weighing 82 kilos is between 2,092,000 and 2,592,000 calories" in twenty- 

 four hours therefore, between 1450 and 1798 calories in the minute. 



i. Elevation of temperature causes dilatation of the cutaneous ves- 

 sels. The skin becomes vividly reddened, soft, and full of fluid, so that 

 it serves as a better conductor of heat and is swollen. The epithe- 

 lium becomes moistened and sweat exudes from the surface. In this 

 way provision is made for augmented heat dissipation, evaporation of 

 the sweat playing an important part in the abstraction of heat. 



The greater the increase in the moisture of the air, the less becomes the evapora- 

 tion from the skin. Accordingly, heat-dissipation must be increased by conduc- 

 tion and radiation. The same amount of heat that is capable of transforming 

 i gram of water at a temperature of 100 C. into steam is equal to that which 

 will raise the temperature of 10 grams from o to 53.67 C. The sweat secreted 

 is of the same temperature as the body; if it be completely converted into vapor 

 it will require first sufficient heat to raise it to the boiling-point and then addi- 

 tionally the amount of heat that will convert it from this point into steam. For 

 purposes of more precise determination there would be required a knowledge of 

 the heat-capacity and of the boiling-point of the sweat. 



The action of cold is to cause contraction of the cutaneous vessels. 

 The skin becomes pale, less soft, deficient in fluid and collapsed. The 

 epithelium becomes dry and permits the escape of no fluid for evapora- 

 tion. In this way dissipation of heat through the skin is diminished. 

 Through the contraction of the muscles of the skin and of the cutaneous 

 vessels, with the displacement of well-conducting fluid and blood from 

 the skin and the subcutaneous connective tissues, loss of heat from the 

 periphery is diminished and heat-conduction transversely through the 

 tissues is rendered difficult. The cooling of the body is lessened through 

 the marked interference with the flow of blood through the skin, in the 

 same way as is the case with a cooling apparatus made of convoluted 

 tubing if the current passing through it is greatly lessened. If, however, 

 the cutaneous vessels undergo dilatation, the. temperature of the surface 

 of the body rises, and the difference in temperature between it and the 

 surrounding cooler medium is increased, and thus the loss of heat is aug- 

 mented. Tomsa has shown that anatomically the arrangement of 

 the fibrillation of the skin is such that every stretching of the fibers 

 effected by the muscles of the skin gives rise to a reduction in the thick- 

 ness of the skin, as a result of which an influence is exerted principally 



