Carbon Chemistry with Vital Phenomena. 351 



The chemistry of cellulose is a case in point. This substance 

 will be found, even to this day, treated by chemists as a well- 

 defined body, of intrinsically fixed characteristics ; whereas 

 physiologists, with special regard to its functions in the living 

 plant, have long since observed it to be capable of many modi- 

 fications, more or less profound, and have not hesitated to 

 regard it as the parent substance of that large class of aro- 

 matic bodies of which tannin is the type. 



Geology had made us acquainted with the very profound 

 modification of cellulosic structures which are seen in coal; and 

 the chemical study of coal in its various forms had revealed a 

 progressive increase in aromatic potentiality ; and yet the 

 obvious generalization of these several results has been widely 

 ignored, the genetic connexion suggested by this large group 

 of naturally occurring substances has been practically neglected, 

 and chemists have remained satisfied with a purely empirical 

 treatment. Taking this connexion as a working hypothesis 

 and investigating the essential relations therein suggested, we 

 feel assured that a much more productive field of inquiry is 

 opened out. The essential difference between coal and cellu- 

 lose is measured by the difference of their products of decom- 

 position by dry distillation: in coal we have the source of the 

 vast series of aromatic compounds which constitute the sub- 

 ject matter of the most important development of our science. 

 Although the constitution of coal is still unsolved, and we 

 cannot yet say to what extent it might be made to yield 

 aromatic bodies by less drastic processes of resolution than 

 that of destructive distillation, yet the general fact that in 

 relation to cellulose it possesses an increased (immediate) 

 aromatic potentiality has been sufficiently established. The 

 nitrogen, further, derived from the proteid matters of the 

 parent tissues exhibits a progressive diminution; and the che- 

 mistry of the formation and decomposition of coal may be 

 considered independently of this element*. It remains there- 

 fore to investigate the conversion of cellulose into substances 

 of the aromatic group of compounds. 



The first link in the chain of development would appear, 

 from the researches of physiologists, to be contained in the 

 phenomenon of the lignification of cellulose structures. In 

 the life of the plant, extreme processes of reduction and oxi- 

 dation, of synthesis and resolution occur simultaneously and 

 continuously. The formation of cellulose and its lignification 

 have been ranged by physiologists on the basis of this anti- 

 thesis. The connexion between lignin and the great group of 



* W. A. Miller, ' Elements of Chemistry,' iii. p. 145, by whom this 

 subject appears to be developed more consequently than by most writers. 



