426 HOMOIOTHERMAL AND POIKILOTHERMAL ANIMALS. 



(rf) Other processes are the formation of heat from the absorption of C0 2 

 (Henry), by the concentration of water as it passes through membranes (Regnault 

 and Pouillet), in imbibition (Matteucci, 1834), formation of solids e.g., of chalk 

 in the bones. After death, and in some pathological processes during life, the 

 coagulation of blood (Valentin, Schiffer), and the production of rigor mortis, are 

 sources of heat. 



207. Homoiothermal and Poikilothermal Animals. 



In place of the old classification of animals into "cold -blooded" and 

 " warm-blooded," another basis of classification seems desirable, viz., the 

 relation of the temperature of the body to the temperature of the 

 surrounding medium. 



Bergmann introduced the word homoiothermal animals for the 

 warm-blooded animals (mammals and birds), because these animals can 

 maintain a very uniform temperature, even although the surrounding 

 temperature be subject to considerable variations. The so-called cold- 

 blooded animals are called poikilothermal, because the temperature of 

 their bodies rises or falls, within wide limits, with the heat of the 

 surrounding medium. 



When homoiothermal animals are kept for a long time in a cold 

 medium, their heat production is increased, and when they are kept for 

 a long time in a warm medium it is diminished. 



Fordyce gave a proof of the nearly uniform temperature in man. A man re- 

 mained ten minutes in an oven containing very dry hot air, and yet the tempera- 

 ture of the palm of his hand, mouth, and urine was increased only a few tenths of 

 a degree. 



Becquerel and Brechet investigated the temperature of the human biceps (by 

 means of thermo-electric needles), when the arm had been one hour in ice, and 

 yet the temperature of the muscular tissue was cooled only 0'2C. The same 

 muscle did not undergo any increase in temperature, or at most 0'2C, when the 

 man's arm was placed for a quarter of an hour in water at 42C. 



If heat be rapidly abstracted or rapidly supplied to the body, so as 

 to produce rapid variation of the temperature, life is endangered. 



Poikilothermal animals behave very differently; the temperature of 

 their bodies generally follows, although with considerable variations, 

 the temperature of the surroundings. When the temperature of the 

 surroundings is increased, the amount of heat produced is increased, and 

 when the surrounding temperature falls, the amount of heat evolved 

 within the body also falls. 



The following table shows very clearly the characters of poikilothermal 

 animals, e.g., frogs (Rana Esculenta), which were placed in air and water 

 of varying temperatures. The frogs were fixed to an iron support, and 

 immersed up to the mouth. The temperature was measured by means 

 of a thermometer introduced through the mouth into the stomach. 



