112 COMPARISON OF VEGETABLE 



mind the idea of an analogy with the circulation 

 of the blood in animals, and a fanciful imagina- 

 tion might see a degree of further likeness to 

 the venous and arterial blood in the two states 

 of the sap. The similarity, however, though it 

 does exist, is but very partial, no one general 

 circuit of the sap throughout the system, as 

 there is of the blood originally propelled from 

 the heart, really taking place. Again the tissue 

 produced and nourished in the two kingdoms, 

 though very analogous in some respects, is by 

 no means identical : the cellular texture of 

 animals differing from the cellular tissue of plants 

 by its structure, which is not actually composed 

 of individual cells, united together by the cohe- 

 sion of their walls, but of " a congeries of ex- 

 tremely thin laminae or plates, variously con- 

 nected together by fibres, and by other plates, 

 which cross them in different directions, leaving 

 cavities or cells."* This cellular texture, how- 

 ever, forms the essential material of the animal 

 fabric generally, as the cellular tissue does of 

 the vegetable. The important chemical diffe- 

 rence between animal and vegetable organized 

 tissue has already been noticed, viz. the pre- 



* Roget's " Anim. and Veget. Physiol." vol. i. p. 99. 



