88 



CHEMICAL CONSTITUTION OF VEGETABLES. 



plants, the other the woody substance, properly so called, filling, 

 and in some sort consolidating the cells. This distinction between 

 these two elements of wood was first made by M. Mohl ; but M 

 Payen was the first who fixed the opinion of chemists and of vege- 

 table physiologists upon the true nature of these immediate princi- 

 ples.* By treating the vegetable tissue in its nascent and still 

 gelatinous state — the unimpregnated kernel of the almond, of the 

 apricot tree, &c., the membranous matter of the cambium of the 

 cucumber, the spongioles of radicles, leaves, wood, &c. — with differ- 

 ent menstrua, M. Payen obtained the cellular tissue in the state of 

 purity, and having an elementary composition almost identical, from 

 whatever source derired ; a fact which may be seen from the fol- 

 lowing table, which gives the composition of cellular tissue from 

 different sources after having been dried at 352° Fahr. 



The primary tissue, consequently, which constitutes the skeleton 

 of wood, is still isomeric or identical in elementary comjKisition with 

 starch. With mineral acids the cellular tissue further undergoes 

 changes which assimilate it with starch ; for on treating it with sul- 

 phuric acid it is changed into dextrine and sugar. 



The composition of the cellular tissue differs considerably from 

 that of the woody fibre as it has hitherto been obtained after the 

 action of solvents, and been examined by preceding chemists. 

 Pure wood or woody tissue consists of the following proportions of 

 elements : 



Dumas, Conipfcs rcndus, vol. vlii. p. 53, 



