XX 



ON THE IDENTITY OF STRUCTURE OF PLANTS AND 



ANIMALS 



Abstract of a Friday Evening Discourse at the Royallnstitiition, April 15,1853 ; 

 Royal Institution Proceedings, i. 1851-4, //. 298 — 302 ; Edinburgh New 

 Philosophical Journal, liii. 1852,//. 172 — 177 



The Lecturer commenced by referring to his endeavours last year 

 to show that the distinction between living creatures and those which 

 do not hve, consists in the fact, that while the latter tend to remain 

 as they are, unless the operation of some external cause effect a 

 change in their condition, the former have no such inertia, but pass 

 spontaneously through a definite succession of states — different in 

 kind and order of succession for different species, but always identical 

 in the members of the same species. 



There is however another character of living bodies — Organisation ; 

 which is usually supposed to be their most striking peculiarity, as 

 contrasted with beings which do not live ; and it was to the essential 

 nature of organization that the Lecturer on the present occasion 

 desired to direct attention. 



An organized body does not necessarily possess organs in the 

 physiological sense — parts, that is, which discharge some function 

 necessary to the maintenance of the whole. Neither the germ nor 

 the lowest animals and plants possess organs in this sense, and yet 

 they are organized. 



It is not mere external form, again, which constitutes organization. 

 On the table there was a lead-tree (as it is called) which, a mere 

 product of crystallization, possessed the complicated and graceful 

 form of a delicate Fern. If a section were made of one of the 

 leaflets of this tree, it would be found to possess a structure optically 

 find chemically homogeneous throughout. 



Make a section of any young portion of a true plant, and the 



