I ONTROL OP BODV l I MP1 R \'i 'i Bl IND I i \n: 719 



warmth or when the region of il orpora striata is artificially warmed, 



the breathing immediately becomes much quicker and deeper, bo thai 

 pulmonic ventilation is greatly increased and much more water is carried 

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

 ties of heal are required Been in the latenl heal of steam). In man this 

 method is. ordinarily, nol of greal importance, bul it may become 

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

 breathing also facilitates cooling by increasing the conduction of heal 

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

 portance of this method of ling has been shown by finding thai after 



the introduction of a tracheal cannula a dog can nol withstand an in- 

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



There are many other questions concerning the control of heat 1 

 from the human body thai mighl be considered, but it is - 

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

 humidity of the air in the control of heal 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 tlio heat-conducting power of the air and therefore tends to c 

 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 tho 

 air is dry than when it is moist. On the dry plains of the Wesl a tom- 

 perature of many degrees below zero causes less bi E cold to be 



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

 perature along the Greal Lakes and in the river valleya 



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 heal loss may be, there can 

 be little doubl thai it is often managed to the detriment of good health. 

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

 diminishes the loss of heal from the body thai the tone and heat-produc- 

 ing powers of the muscular system are lowered \ • only does this 

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

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



also l me constricted and the skin bloodless and ••pasty." I- 



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

 little to do the heat-regulating mechanism g< - it wore, oul 



