CH. VIII.] THE DISEASES OF PL-\^•TS. 247 



adopting a totally antagonist opinion, estimate vege- 

 tables as bodies, only somewhat more organized 

 than crystals, but like these entirely and micon- 

 troledly subject to chemical and mechanical changes. 



Each of the foregoing extreme opinions is simi- 

 larly eiToneous, as ^^ill have been gleaned from the 

 facts mentioned in preceding pages, and as vrill more 

 clearly appear from those -^'hich now follow. The 

 gradation from reason to instinct, from instinct to 

 inanimation, might easily be she^Ti to be as gradual 

 as are the transitions of light in om* climate from the 

 noontide to the midnight of a summer's day. But 

 we must, in this volume, confine our attention to 

 that section of creation commencing from the close 

 of the animal classes in the zoophyte, and termi- 

 nating where inorganic matter commences in the 

 crystal, and the details here given must be directed 

 specially to demonstrate how closely it approaches, 

 how indistinctly it is divided from, the former. 



Let us first consider the comparative composition 

 of animals and plants as revealed by the researches 

 of the chemist, and it must be somewhat startling 

 even to the most sceptical to find that their consti- 

 tuents are identical. Carbon, hydrogen, oxygen, 

 nitrogen, sulphm', phosphoiTis, acids, alkalies, earths 

 and metals are the components of both. 



Nitrogen was considered as a constituent, mark- 

 ing, by its presence, animal from vegetable matters ; 



