160 PROCESS OF NUTRITION. CHAP. III. 



of being made to inhale an unlimited quantity of 

 oxygene many times the size of their own volumes* 

 Why ? What is the cause of this apparent anomaly ? 



Why are not leaves which are made to vegetate in 

 the dark, saturated with oxygene in the open air as 

 well as in confined atmospheres ? and why does their 

 alternate exposition in the receiver and in the open 

 air give them the property of inhaling an unlimited 

 quantity. The truth is, that the inhalation of this 

 unlimited quantity is a mere deception, produced by 

 the action of the atmospheric air upon the carbonic 

 acid contained in the leaves. The air of the atmos- 

 phere has a chemical affinity for carbonic acid gas, 

 as has been already shown upon the authority of 

 Bertholet,* and abstracts, by consequence, a portion 

 of it from the leaf which it thus prepares for com* 

 mencing anew the process of inhalation ; so that 

 however long the alternate change of exposition 

 may be continued, there is no accumulation of car- 

 bonic acid or of oxygene. 



inhalation But the inhalation of oxygene seems to depend 

 on P the ant u P on tne structure and organization of the leaf; for 

 structure Saussure found with regard to the Cactus what 



of the leaf. 



Senebier found with regard to other leaves that 

 when they were cut into pieces and pounded in a 

 mortar, so as to destroy their organization, and then 

 placed under a receiver filled with common air, no 

 inhalation took place ; though they formed carbonic 

 acid gas, by the combination of the carbon which 

 * Mem. tic rinst. Nat. torn. iii. 



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