existing in vegetable structures. 75 



only mere accidental traces of saline matter ; for the other 

 elements of vegetable tissue, are capable of forming volatile 

 combinations, under the influence of the heat employed. — 

 Thus, the hydrogen and nitrogen unite, and are evolved as 

 ammonia; the carbon unites with oxygen from the air, to form 

 carbonic acid ; and the remaining hydrogen with the oxygen 

 of the plant, or of the atmosphere, to form water. All these 

 new combinations escape in a gaseous form, and leave behind, 

 not mere insignificant traces of saline matter, but the genuine 

 skeleton of the vegetable tissue employed, formed of siliceous 

 and saline matter, in which may be observed the most deli- 

 cate forms of the organic structure ; spiral vessels, ducts, and 

 the outline of cellular tissue being distinctly visible, notwith- 

 standing that every trace of the organic products of which 

 they are generally considered to be formed, has been expelled 

 by the heat employed in effecting the incineration. 



For this highly interesting and valuable observation we are 

 undoubtedly indebted to the ingenious researches of Raspail, 

 whose labours, it is much to be regretted, have neither in this 

 country, nor in his own, attracted that degree of notice and 

 attention to which their importance justly entitles them ; a 

 circumstance which may be attributed partly to the peculiar 

 style in which his works are written, and partly to the bitter 

 and sarcastic spirit with which they are, unhappily, imbued. 

 One of this philosopher's experiments is peculiarly worthy of 

 attention, as well from its elegance and interest, as from the 

 light which it throws on the difficulties of the subject under 

 consideration. If we take a fragment of the epidermis of a 

 plant, and press it flat upon a plate of glass, after having sub- 

 mitted it to the action of a dilute acid, for the purpose of re- 

 moving any saline matter incrusting its tissue, and examine 

 it with the assistance of a microscope, we shall observe its 

 cellular structure with the utmost readiness. Let us now sub- 

 mit this piece of glass, with the fragment of epidermis, to a 

 red heat, and, when cold, again subject it to microscopic ex- 

 amination ; and so perfect will the structure of the epidermis 

 appear, that we can scarcely believe that its organic matter 

 has been destroyed, all its cellular tissue remaining imprinted 

 on the glass, in a skeleton formed chiefly of phosphate and 

 carbonate of lime ; for the addition of a single drop of diluted 

 hydrochloric acid, dissolves these salts, and causes every ap- 

 pearance of organization to vanish.* 



*" Mais une seule goutte d'acicle, tres etendu, suffit pour detruire cette 

 illusion ; et ces reticulations y disparaissent avec rapidite." 



Raspail; — Nouv. Syst. de Chim. Organiq. p. 529. 

 g3 



