88 



that it does occasionally in it, and constantly in other plants. 

 Thai in those parts of the leaf which had been removed from 

 the parent plant, and in which the circulation was general, 

 vitality had not absolutely departed, as one or two of them 

 had been known to grow after the separation.* The effects 

 of certain vegetable poisons in entirely destroying the circula- 

 tion, while others only affect it a short time, their influence 

 passing away under favourable circumstances, afford strong 

 evidence of its dependence upon vital causes. 



" If a sensitive plant were treated in the same way as the 

 valisneria, its irritability would be equally destroyed by prussic 

 acid and opium, and it would be recovered equally when 

 removed from their influence. The vital character of the 

 phenomenon in the one could not be established, as it had 

 been in the former, without allowing it in the latter." 



The author then adduced some instances of circulation in 

 the animal world which seemed analagous to that in the valis- 

 neria, and which could only be explained by presuming the 

 existence of a vital and unknown force. 



"In the chick 'the area vasculosa is beset with dark aggre- 

 gated masses ; single isolated points then appear ; between 

 these, clefts are formed that, by and by, run together and form 

 channels, which unite in meshes with one another ; in these 

 channels a clear, colourless, or extremely pale liquid, of a 

 yellow colour, can, by and by, be distinguished in motion — 

 this is the blood. Along with these changes the development 

 of the heat has been advancing? &c.j i. e., the motion com- 

 menced in the blood independent of the heart. 



"Again, in a more advanced state of existence, the pheno- 

 menon of circulation has been witnessed independent of a heart. 



"Mr. Hassall has stated, in his Microscopic Anatomy, that 

 he has witnessed a most regular, and constant circulation, in 



* The Rev. T. Dwyer, to whom the slips exhibited at the Society were giveD, lias 

 since informed the author, that one of the green ones has sent forth roots, and begun 

 i" exist as an independent plant, ovidently showing that ii bad retained its vitality. 



