REJUVENESCENCE IN NATURE. 217 



in the mterchanges of material of the animal organism, 

 formation and deformation intermix in simultaneous 

 occurrence, dissolving and newly shaping in the same 

 epoch, the two processes are more separated in the plantj 

 running into one another in periodical alternations. In 

 the Vegetable kingdom, as in the Animal, the nitrogenous 

 substances (proteine and the substances allied to it) form 

 the especial substratum and active medium of the vital 

 activity,* while the unazotised substances, rich in carbon, 

 play a more passive part in the organism, on the one 

 hand protecting, on the other limiting, narrowing, stupe- 

 fying, and even extinguishing the vital force. The 

 animal organism frees itself from the superabundance of 

 carbonaceous substances, which it receives for the most 

 part already formed in its food, through the uninterrupted 

 process of respiration, in which the carbon is destroyed 

 (burnt) by the aid of the oxygen derived from the atmo- 

 sphere, and excreted in the form of gas. It is different 

 with the plant ; it does excrete the substances rich in 

 carbon formed in the internal organism of the cell, out 

 of the cell-sap, not, however, destroying them, but depo- 

 siting them either as organic structures on the confines of 

 the cell-organism (formation of membrane from cellulose, 

 and the allied substances, gelin, amyloid. Lichen-starch, 

 &c.), or it secretes them in the interior of the cell itself 

 as globular, frequently laminated masses (starch or 

 inuhne), or in the form of drops (fixed oils). The forma- 

 tion of the cellulose membranef is especially characteristic, 

 in this respect, of the plant, securing to the cell-formation 

 of the plant, in all cases, its peculiar separateness and 

 independence, however varied the mode of ultimate 



* According to Payen, all young organs of plants, in their earliest stages 

 of development, contain a predominance of nitrogenous substances. 



f Cell-membranes formed of cellulose have hitherto been found in 

 the animal kingdom only in the sac-shaped envelopes of the Ascidia. See 

 Schmidt, " Zur Vergleichenden Physiologie der wirbellose Thier," (1845) 

 Transl. in " Taylor's Scientific Memoirs ;" Lowig and Kolliker, " De la 

 Composition et de la Structiire des Enveloppes des Tuniciers," ('Ann. 

 des Sc. Nat.,' 1846, p. 193.) 



