TEMPERATURE AND LIFE. 413 



to man. There are differeuces iu degree, but the fact is universal. It 

 remains for us to prove that this is not only the rule with animals, but 

 is also true wherever there is vegetable life, constituting in fact an 

 inherent function in all animate matter. 



Plants respire, consequently they generate heat. This Is an ascer- 

 tained fact of which proof has been given by numerous experiments. 

 The cholorophyllic function, which effects a decomposition of carbonic 

 acid in the oxygen which is exhaled, and iu carbon which is incorporated 

 in the tissues, has, for a considerable time, obscured the true manner 

 of respiration, making it appear that vegetables respire in an entirely 

 different way from animals. The process is the same in the two classes 

 of organisms. To assure ourselves of the fact, however, it is necessary 

 to eliminate the chlorophyllic function by having recourse to a particu- 

 lar arrangement; experimenting upon plants without chlorophyll, or 

 upon chlorophyllic plants kept in darkness — the chlorophyllic function 

 acting only in light. In taking the above precautions, we establish 

 the fact that respiration exists among all plants — with more activity, 

 it is true, in young plants than in older ones, in plants which are in 

 course of development, rather than those which have already attained 

 their full growth. This respiration, as in animals, consists of chemical 

 phenomena. It is caused by an absorption of oxygen, and a combina- 

 tion of that gas with the tissues of the plant, by which heat is produced. 

 As observation has demonstrated to us, everything that has life gener- 

 ates heat bj'^ reason of the chemical phenomena which accompany life. 

 The germination of seeds, for example, does not occur without this 

 evolution of heat. To assure ourselves of this, let a thermometer be 

 placed in the midst of a quantity of seed in process of germination, 

 taking care to insure the elimination of carbonic acid in proportion as 

 it is produced — for it arrests respiration and calorification. The ther- 

 mometer will be seen to rise 5°, 10°, 15°, and 20° C. The generation of 

 heat in this case is therefore considerable. Various experiments made 

 with seeds have substantiated the conclusion. Flowers also produce a 

 remarkable amount of heat, the truth of which Lamarck was the first to 

 establish. It is with flowers of certain aroides that experiments have 

 been most successful, and which have furnished the most exact data. 

 The temperature of the spathe of these plants when in full flower indi- 

 cates a generation of considerable heat, presenting sometimes an excess 

 of 5°, 10°, and 15° over the surrounding temperature. To show that 

 this calorification is a result of respiration, let a flower be covered with 

 oil in order to exclude the oxygen in the air, or let it be placed in an 

 inert gas from which all oxygen has been exhausted (nitrogen for in- 

 stance), and its temperature will be reduced to almost nothing; combus- 

 tion is retarded if not entirely suppressed. Very delicate experiments 

 have established beyond a doubt that a close correlation exists between 

 the supply of oxygen and the amount of heat produced, the latter being 

 proportionate in intensity to the quantity of oxygen absorbed. 



