THE SUMMER HEAT OF CITIES. 439 



the temperature of the place is raised, as happens almost daily in 

 the summer months in cities. 



From the preceding facts we may conclude that, as long as the 

 body continues in health, the " heat-regulating power," which con- 

 stantly tends to preserve an equilibrium of temperature, is capable 

 of resisting the ordinary agencies that, operating externally or inter- 

 nally, exaggerate the heat-producing conditions, and thus destroy 

 the individual. But if the person is suffering from a disease which 

 weakens the " heat-regulating power " these deleterious agencies, 

 which the healthy person may resist, will readily overpower the 

 already quite exhausted heat-regulating forces, and he perishes by 

 combustion. It is very evident that in an organism having compli- 

 cated functions, like that of man, and subject to such a multitude of 

 adverse influences, the balance between health and disease must be 

 very nicely adjusted. Too great an elevation or too great a depression 

 of temperature may destroy the " heat-regulating power," and dis- 

 ease or death will be the consequence. Or this " heat-regulating 

 power " may be weakened or destroyed by causes generated within 

 the body, or received from without, and the heat-producing agencies 

 are then under influences which may prove to be powerfully de- 

 structive forces. 



It will not now be difficult to understand in what manner high 

 temperature affects the public health of large cities. Evidently in 

 the direct action of heat upon the human body we have the most 

 powerful agency in the production of our great summer mortality. 

 While sunstroke represents the maximum direct effect of solar heat 

 upon the human subject, the large increase of deaths from wasting 

 chronic diseases and diarrhceal affections., of children under one year 

 of age and persons upward of seventy years of age, shows the terrible 

 effects of the prevailing intense heat of summer upon all who are 

 debilitated by disease or age and thereby have their " heat-regulating 

 power " diminished. The fact has been established by repeated ex- 

 periment that when solar or artificial heat is continually applied to 

 the animal the temperature of its body will gradually rise until all 

 of the compensating or heat-regulating agencies fail to preserve the 

 equilibrium, and the temperature reaches a point at which death 

 takes place from actual combustion. In general, a temperature of 

 107° F. in man would be regarded as indicating an unfavorable ter- 

 mination of any disease. In persons suffering from sunstroke the 

 temperature often ranges from 106° F. to 110° F., the higher tem- 

 perature appearing just before a fatal termination. 



The indirect effects of heat appear in the production of poi- 

 sonous gases which vitiate the air and render it more or less preju- 

 dicial to health. Decomposition of all forms of refuse animal and 



