354 Messrs. Cross and Bevan on the Correlation of 



such as the resins, it is surely incumbent upon chemists to 

 recognize the call to investigate the natural origin and history 

 of the carhon compounds, and first of all in their relation to 

 cellulose. We know the objection in the minds of many to 

 forsake the familiar landmarks of positive physical definition, 

 such as crystallization and molecular volume, for a province 

 where the absence of the criteria hitherto regarded as all im- 

 portant makes the results to be obtained appear to that extent 

 conjectural; we know indeed that the objection in many cases 

 takes the more active form of almost refusing credence to any 

 results obtained with substances that are amorphous and essen- 

 tially transitional ; and against this attitude a most emphatic 

 protest is to be lodged. Arithmetic cannot cope with the 

 physics of living matter; and we shall need to promote our 

 equations and constants several degrees before we can include 

 its chemical phenomena. Moreover the purity of substances, 

 as the only condition in which to be approached by the che- 

 mist, will need a very elastic interpretation in presence of 

 matter undergoing differentiation; and such properties as have 

 hitherto been regarded as affording the only guarantees of 

 purity will have no place in a vast amount of research that 

 requires to be done. We clearly recognize the large amount 

 of work already accomplished by isolated effort in this depart- 

 ment of chemical science ; but these remain for the most part 

 uncorrelated, and, as a glance at the text-books will show, in 

 a great measure unrecognized. 



Not only have the suggestions of physiologists in regard to 

 the probable origin of aromatic substances in the plant been 

 but little developed by chemists, but the equally important 

 correlation of the carbohydrates with the fats, which follows 

 from their physiological equivalence, still lies without our 

 science. Here also a transformation in series is suggested, 

 the intermediate terms of which are probably to be found in 

 cutin and analogous bodies, constituents of cork structures. 

 The changes through which the transition is accomplished are 

 probably very profound, more so than in the conversion of 

 cellulose into Iignin. Of the mechanism of the conversion we 

 are as yet entirely ignorant : but we have the conviction, in 

 this as in every other case, that the vital force of the plant 

 operates through the same materials and forces which lie at 

 our disposition, and that its results can therefore be studied 

 and in some measure reproduced. 



The study ut these transformations must, in the first 

 instance, of course be analytical; and most important correla- 

 tions will follow from a comparative examination of the pro- 

 ducts of resolution of plant-substances. Take, for instance, 



