CONTROL OF. BODY TEMPERATURE AND FEVER 719 



warmth or when the region of the corpora striata is artificially warmed, 

 the breathing immediately becomes much quicker and deeper, so that 

 pulmonic ventilation is greatly increased and much more water is carried 

 out as vapor with the expired air. To vaporize the water large quanti- 

 ties of heat are required (seen in the latent heat of steam). In man this 

 method is, ordinarily, not of great importance, but it may become so 

 when sweating is interfered with, as in ichthyosis. The more rapid 

 breathing also facilitates cooling by increasing the conduction of heat 

 from the mucous membranes of the tongue, mouth, throat, etc. The im- 

 portance of this method of cooling has been shown by finding that after 

 the introduction of a trachea! cannula a dog can not withstand an in- 

 crease of external temperature nearly so well as a normal animal. 



There are many other questions concerning the control of heat loss 

 from the human body that might be considered, but it is scarcely nec- 

 essary to do so here. It should be added, however, that the relative 

 humidity of the air in the control of heat loss has a different significance 

 when the temperature is high from that when it is low. High relative 

 humidity at high temperatures, as we have seen, interferes with evapora- 

 tion of sweat, whereas high relative humidity at low temperatures in- 

 creases the heat-conducting power of the air and therefore tends to cool 

 off the surface of the body by greater conduction. It is on this account 

 that it is much more comfortable to live at a low temperature when the 

 air is dry than when it is moist. On the dry plains of the West a tem- 

 perature of many degrees below zero causes less sense of cold to be ex- 

 perienced than in the moist atmosphere at a considerably higher tem- 

 perature along the Great Lakes and in the river valleys. 



THE CONTROL OF TEMPERATURE 



In the case of man the body temperature is very largely under volun- 

 tary control, as by the choice of clothing and the artificial heating of the 

 room. Desirable as this voluntary control of heat loss may be, there can 

 be little doubt that it is often managed to the detriment of good health. 

 Living in overheated rooms during the cooler months of the year so 

 diminishes the loss of heat from the body that the tone and heat-produc- 

 ing powers of the muscular system are lowered. Not only does this 

 diminish the resistance to cold, but it causes the food to be incompletely 

 metabolized so that it is stored away as fat. The superficial capillaries 

 also become constricted and the skin bloodless and "pasty." It is not 

 looks alone that suffer, however, but health as well, for by having so 

 little to do the heat-regulating mechanism gets, as- it were, out of gear, 



