494 BIOLOGICAL PHYSICS 



possessed by every human body in a state of health, and 

 the disturbance of which leads to a rise or fall, as the case 

 may be, or to the development of a more or less pro- 

 longed pathological departure from the normal tempera- 

 ture. The basis of this regulative machinery is, we 

 conclude, located in the skin externally and the air- 

 passages internally, whose outlets, open or closed, are 

 regulated by nerve and muscle, agencies which determine 

 the proper amount of insensible transpiration and sensible 

 perspiration and respiratory output respectively passing 

 through them, and, so long as the conditions of health 

 are maintained, sustain the standard of the body tempera- 

 ture at 98-4 F. Thus, we find that a healthy human 

 body in a state of res f, does not require the free opening of 

 its cutaneous apertures, provided a suitable temperature 

 of its environment prevails, hence we conclude that the 

 ordinary external and internal radiation suffice to maintain 

 the natural, or normal, 98-4 F. We find also that a 

 human body in a state of activity requires, for the main- 

 tenance of 98*4 F., a more or less free exercise of the 

 functions of transpiration and perspiration, in addition to 

 that of ordinary internal and external radiation. 



The general cutaneous surface of the body is constantly, 

 more or less, employed in this function, and is to a great 

 extent, although not by any means totally, sufficient for 

 the vital function of heat or temperature regulation, the 

 mucous and certain serous surfaces, as well as gland 

 textures, being also largely utilised for the same purpose. 

 Radiation is constantly, therefore, in evidence from the 

 surfaces of the body, wherever they are reached by the 

 surrounding air whether that air is above or below the 

 temperature of the body in question hence radiation is a 

 relative process, being regulated to a great extent by the 

 prevailing surrounding and inhaled air, or external 

 atmospheric temperature ; besides, it seems to us not to- 

 be regular or identical in its amount throughout the area 

 or extent of its occurrence, but to prevail to a fuller 

 extent over certain areas in particular, such as, for instance, 

 the palms of the hands and the soles of the feet, which, 

 being usually exposed to contact with relatively cold 

 surfaces, radiate their heat much more rapidly, in conse- 



