200 



Lord Kelvin : Animal Thermostat. 



" To determine whether the cold produced in this instance 

 depended solely on the evaporation from the surface, increased 

 by the energy of the vital principle, a living and dead frog- 

 were taken at 75°, and were immersed in water at 93°, the 

 living frog being placed in such a situation as not to interrupt 

 respiration *. 



Min. 



Dead Frog. 



1 



1 Living Frog. 



! 





o 



1 o 1 



Inl 



85 



81 



„ 2 



8S£ 



85 



.. 3 



90£ 



87 



.. f) 



9H 



89 



„ 6 



91-| 



89 



,, 8 



9H 



89 



" ; These experiments prove, that living frogs have the 

 faculty of resisting heat, or producing cold, when immersed 

 in warm water : and the experiments of Dr. Fordvce prove, 

 that the human body has the same power in a moist as well 

 as in a dry air : it is therefore highly probable, that this 

 power does not depend solely on evaporation. 



" It may not be improper here to observe, that healthy 

 frogs, in an atmosphere above 70°. keep themselves at a lower 

 temperature than the external air, but are warmer internally 

 than at the surface of their bodies ; for when the air was 77°, 

 a frog was found to be 68°, the thermometer being placed in 

 contact with the skin ; but when the thermometer was intro- 

 duced into the stomach, it rose to 70-J°. It may also be 

 proper to mention, that an animal of the same species placed 

 in water at 61°. was found to be nearly 61^° at tbe surface, 

 and internally it was 661°. These observations are meant to 

 extend only to frogs living in air or water at the common 

 temperature of the atmosphere in summer. They do not 

 hold with respect to those animals, when plunged suddenly 

 into a warm medium, as in the preceding experiments. 



" To determine whether other animals also have the power, 

 of producing cold, when surrounded with water above the 

 standard of their natural heat, a dog at 102° was immersed 

 in water at 114°. the thermometer being closely applied to 

 the skin under the axilla, and so much of his' head being- 

 uncovered a> to allow him a free respiration. 



* In the above experiment the water, by the cold frogs and by the 

 agitation which it suffered during their immersion, was reduced nearly 

 to 91£°.— Orig. 



