Hi BIOLOGY. [Book vii. 



reduced to its minimum; it is a hibernant slumber much more 

 profound than that of animals. The nutritive exchanges are 

 then, in most cases, too unimportant to determine an appreciable 

 elevation of the temperature. As to estival observations, they 

 must also be cautiously judged. The plant has not, like even the 

 lowest animal, a perfected circulatory system, which everywhere 

 equalises the temperature. In the vegetal, each region, each 

 tissue, each organ, enjoys a sufficiently large independence; 

 the federative rule is there much more accentuated than in 

 the animal. 



The centre of trees, the hardened ligneous part, is half 

 mineralised, and any thermometrical instrument introduced 

 into this half dead region can indicate little or no elevation of 

 temperature. It would be necessary to take in summer, during 

 full vegetative movement, the temperature of the cambiiun, of 

 the intermediary layer between the aubier and the bark. It is 

 certain that, at all times when, in any part whatever of a vegetal, 

 the phenomena of nutrition, .of development, of transformation, 

 acquire a certain degree of intensity, the local temperatiu-e rises 

 much. It is sufficient to signalise, in support of this assertion, 

 the thermometric phenomena which accompany germination and 

 florescence. 



However, it is specially in the animal kingdom that the thermic 

 independence of the organised being is clearly indicated. But 

 here again the distinctive temperature of the animal is higher, 

 less subject to exterior thermometric fluctuations, in proportion 

 to the perfection of the species. Professor Valentin, who has 

 noted the numerical proportions of the organic temperature in the 

 principal invertebrated groups has found on an average the excess 

 of the animal temperature over the exterior medium to be : — • 

 In the Polypi 0", 20 



