436 THE REGULATION OF TEMPERATURE 



blooded animals possess by reason of their higher temperature are 

 due to the well-known fact that most chemical and some physical 

 reactions are increased in rate by increase of temperature (see 

 Temperature Coefficient). They also are free from constant 

 fluctuations of temperature. Against this must be placed the fact 

 that they have to maintain a temperature greater than their 

 environment by about 20° C. 



Honioiothennic Animals maintain a constant temperature. 

 Mammals and Birds . . . Birds . . . about 42° C. 



Adult and not during hiberna- f Mammals (except man) ,, 39° C. 

 tion or activity . . . ( Man . . ,, 37° C. 



II eterothermic or Poikilothermic Animals. 



{a) Lethal temperature, about New born Homoiothermes. 



20° C. The young of rats, mice and man 



are practically poikilothermic, and 

 maintain an internal temperature 

 of from 0-01 to 3-0° C. above the 

 temperature of the environment. 

 (6) Hibernation starts when Hibernating animals, 

 temperature falls to about 

 20° C. 

 (c) Still active below 20° C. Eeptiles, Batracia, Fish, Molluscs, 



Insects, etc. 



Of all animals, birds have the highest temperature. For example, that of 

 the chicken is about 43-8° C. : of mammals, the rabbit and the fox have a 

 temperature as high as 40° C, while the horse and the elephant come low on 

 the scale with 37-6° C. 



In health, the temperature of the human body varies so little 

 from the normal value of 37° C. (98-4° F.) that temperature is 

 regularly taken as a clinical indicator and any fluctuation from 

 the normal points to the employment of remedial measures. 



Instruments Used to Indicate Animal Temperature. 



(«) Mercury thermometer. 



(/)) Electrical resistance thermometers. 



{(•) Thermo-electric couple (Thermopile). 



(rt) The thermometer was probably invented by Galileo (1603), and was 

 first used clinically by Sanctorius (1626), who reported the temperature 

 of a fevered man. 



The clinical thermometer is an adapted form of the common mercurial 

 thermometer having, (1) a long cylindrical reservoir to admit of rapid attain- 

 ment of equilibrium between body and mercury. (2) A small bulbous part 

 just above the mercury reservoir to catch the mercury driven out of the 

 reservoir by the expansion due to the increase in temperature to 34° C. 

 (3) A small bore capillary graduated from 35° C. to 45° C. to admit of reading 

 to a tenth of a degree, and finally, (4) another bulbous part to catch any 



