154 M. Dutrochet on the 



plunged in water. The relative cold of the animal placed in 

 the open air arises, therefore, from the coldness produced on 

 its surface by evaporation. 



The tadpoles of the frog presented no appreciable degree of 

 vital heat. 



Bufo ohstetricans^ observed in the open air, was found colder 

 than that medium by 1°.35 F (| of a cent, degree) ; in air sa- 

 turated with moisture, its proper heat was 0°.22 of a degree 

 of F. (0°.12 Cent.). Its tadpole offered no appreciable vital 

 heat. 



The vital heat of the grey lizard (Lacerta agilis^ Linn.) has 

 been estimated by Czermak to be, from 2''.25 F. to 14°.61 F. 

 (from 1°.25 0. to 8°.12 C.) The striking difference in the re- 

 sults obtained, leads us to suspect that there must have been 

 some error. In my own experiments, I have found that this 

 same lizard, in the open air, was colder than the surrounding 

 medium from 0°.32 F. to 0°.305 F. (0M8 0. to 0°.20 C). In 

 air saturated with water, the vital heat appeared to be 0°.38 

 of a degree of Fahrenheit (0°.21 of a cent, degree). 



It will be remarked, in these observations, that the feebler 

 the vital heat is in reptiles, the more decidedly they are aqua- 

 tic. The lizard, which has the greatest degree of heat of the 

 three reptiles made the subjects of observation, inhabits dry 

 places ; the toad frequents holes in moist earth, and its vital 

 heat, inferior to that of the grey lizard, is higher than that of 

 the frog which lives in water. Finally, the tadpoles, which 

 live exclusively in water, have such a low degree of vital heat, 

 that it cannot be appreciated by any thermoscopic means. 



Fishes. — I describe in my memoir the researches made by 

 various observers on the vital heat of fishes ; and shall refrain 

 from introducing them again in this extract. The result of 

 these researches assigns pretty generally to fishes, a vital heat 

 somewhat higher than the water in which they live. Certain 

 observers, however, of higb. repute, have found their tempera- 

 ture to be similar to that of the surrounding water. Such was 

 the conclusion arrived at by MM. Humboldt and Provencal, 

 by MM. Prevost and Dumas, and by M. Berthold. The only 

 fish which I have subjected to experiment, is the Cyprinus 

 alburnus, and I have always found it, when in water, preserve 



