24 MINERAL KINGDOM. 



their food in the earth, and some of which may be 

 turned inside out, like a glove, without any disturbance 

 of their ordinary functions. The most satisfactory re- 

 mark I have for a long time met with on this difficult 

 subject is that of M. Mirbel, in his Traite cV Anatomic 

 €t de Physiologie Veg Hales ^^ a work I shall often have 

 occasion to quote. He observes, vol. I. p. 19, " that 

 plants alone have a power of deriving nourishment, 

 though not indeed exclusively, from inorganic matter, 

 mere earths, salts or airs, substances certainly incapable 

 of serving as food for any animals, the latter only feeding 

 on what is or has been organized matter, either of a 

 vesretable or animal nature. So that it should seem to 

 be the office of vegetable life alone to transform dead 

 matter into organized living bodies." This idea ap- 

 pears to me so just, that I have in vain sought for any 

 exception to it. 



Let us however descend from these philosophical 

 speculations to purposes of practical utility. It is suffi- 

 cient for the young student of Natural History to know, 

 that in every case in which he can be in doubt whether 

 he has found a plant or one of the lower orders of ani- 

 mals, the simple experiment of burning will decide the 

 question. The smell of a burnt bone, coralline, or 

 other animal substance, is so peculiar that it can never 

 be mistaken, nor does any known vegetable give out 

 the same odour.(l) 



* Published at Paris two or ihree years since, in 2 vols. 8vo. 



(1) [It has been remarked that some vegetable products, such 

 as the gluten of wheat, caoutchouc, and the juice ofthe papaw 

 tree ; give out in burning nearly the same peculiar odour which 

 is afforded by animal matter.] 



