On Ihc Philosophy of Nature. 153 



represented his own investigations in general, and in particular 

 his idea of the unity of organic composition, as a proof of the 

 great results to which a conception a priori might lead, he pro- 

 tested against such an assertion ; and, after giving an account of 

 his discovery, shewed that it was the result of the generalization 

 of a series of particular researches, and of observations made 

 with all due care. 



It was by following this course that the author succeeded in 

 placing his law of the unity of organic composition among the 

 number of established principles. The details into which he 

 entered on this subject appear to us worthy of attention. 



He first replied to those who think they see some resemblance 

 in his principles of the unity of organization to the old idea, that 

 all the beings of nature were created in vieza q/'each other, and 

 shewed how bis great principle differs from this hypothetical 

 and insignificant proposition. 



But, it will be said, is not the philosophical resemblance of 

 animated beings an idea that has been debated since the days of 

 Aristotle ? Undoubtedly it is ; but the question was far from 

 being solved : and the author himself, when he took it in hand, 

 set out from considerations which would have led him a priori 

 rather to admit two types of organization than one only. Con- 

 sidering the important office which respiration performs in the 

 life of organized beings, and struck with the incontestible idea 

 that the food is only converted into animalized substance, in con- 

 sequence of the phenomena of respiration, and under its influence, 

 he would have been led to think that organized beings separate 

 into two very distinct classes, according as they respire in media 

 so essentially different as air and water. But observation, and 

 observation alone, apprised him that this is not the case, and 

 that there is only a single being capable of being modified 

 according to circumstances, so as to live in air or in water. 



Consider the vertebrate animals, for example : they are evi- 

 dently constructed in a twofold point of view. Their embryo 

 presents the principle of two respiratory organs, so that if these 

 organs are equally developed, as in the amphibia, they exist to- 

 gether in the adult animal without injuring it, and, on the con- 

 trary, serve it successively in their respective medium. Let one 

 of these organs predominate over the other, there results an ani- 



