ELEMENTAEY EXPERIMENTAL PHYSIOLOGY 



93 



water at room temperature (15 C.). Place two jars of water in the 

 thermostat, and let the water of one jar be covered with a layer of oil. 

 This jar, owing to the prevention of evaporation, will rise more quickly 

 in temperature. 



Loss of Heat. Observe the diminution in temperature of a jar 

 of boiling water when exposed for five minutes to room temperature. 

 Contrast the diminution of temperature during similar periods of time 

 when the jar is jacketed with (1) a cotton bag (2) a flannel bag. 

 Clothes diminish the loss of body-heat by entangling layers of 

 stationary air and surrounding the body with these layers. Conductors 

 of heat and convection currents are stopped by the stationary air in the 

 clothes. Wool garments entangle more air than cotton. Fur and 

 feathers act in the same way. A rabbit covered with tar or varnish 

 dies (unless clothed) owing to the loss of heat. A man is able to 

 regulate his temperature under such conditions. 



Effect of Anaesthesia on Body Temperature. DEMONSTRATION. 

 A small mammal is anaesthetised with chloral or urethane after its 

 rectal temperature has been taken. The animal is laid on the table 

 with its limbs spread out. In the course of an hour the rectal tempera- 

 ture may fall three or four degrees. This is chiefly due to the cessation 

 of muscular movement. The same effect follows curarisation ; section 

 of the spinal cord in the lower cervical region ; the administration of 

 alcohol. Alcohol produces cutaneous vaso-dilatation. It is important 

 to protect anaesthetised patients from exposure to cold. Drunkards 

 who fall asleep on the roadside on a winter's night are easily frozen to 

 death. Large doses of these drugs paralyse the central nervous system 

 which regulates the temperature of the body. 



p.m. 



789 10 11 12 12 3456 789 10 11 12 12 3456 7 



C. 



Fio. 89s. Daily variation of Temperature of Man. (M.S.P.) 



