CHEMICAL SYNTHESIS 13 



some compounds as compared with others. As long, however, as it is 

 borne in mind that the importance of a compound is not measurable 

 by the number of pages occupied by records of its mode of occurrence 

 or of its synthetical production but little harm is likely to arise from 

 this circumstance. It will be evident that such discrepancy is due to 

 the fact that some compounds have lent themselves more readily to 

 chemical investigation than others that some have been found only 

 in a limited number of animal or vegetable products, while others are 

 widely distributed, or again, that some compounds are synthesisable 

 from a few generators only, while others can be synthesised from 

 a multiplicity of generators. Thus cymene [6] and benzyl alcohol [54] 

 occupy the large amount of space that has been devoted to them 

 because they happen to offer the first opportunity for dealing with the 

 syntheses of benzene and toluene respectively, these hydrocarbons 

 being required in many subsequent syntheses. Chemists will, of course, 

 regard such cases in true perspective, although the caution herein 

 conveyed may perhaps be necessary for physiologists who have no 

 special knowledge of organic chemistry. Had benzene and toluene 

 occurred as such in the free state in nature they would of course have 

 been given place among the vital products and had their syntheses 

 recorded in the usual way. 



In view of the improbability of the derivatives of such hydrocarbons 

 as benzene or toluene being synthesised from the hydrocarbon by the 

 living organism it has not been even considered justifiable to include 

 their atomic complexes among the vital products. In fact, in the 

 present state of knowledge, it would be impossible to draw up a satis- 

 factory scale showing the importance to the vital economy of the 

 various synthetical products the more especially since, as already 

 stated, the majority of these are of the nature of down-grade materials. 

 The compounds of fundamental importance in vital chemistry, such as 

 enzymes and albuminoid substances, have not yet been produced in the 

 laboratory, so that chemical synthesis from the biochemical point of 

 view may be said to have been hitherto confined to the lower orders 

 of combination. Even the classification into the main groups of 

 hydrocarbons, alcohols, &c., although convenient for practical purposes, 

 is from the biocentric standpoint purely artificial, and must be taken 

 rather as an expression of imperfect knowledge than of biochemical 

 reality. When with the progress of discovery it becomes possible to 

 construct schemes showing the genetic or evolutional inter-relations 

 among vital products, then will the time be ripe for discussing on 

 a scientific basis the order of importance of the various organic com- 

 pounds in the cycle of vital operations. When our knowledge has 

 reached this level it may be confidently asserted that the biochemical 

 relationships will be found to be quite different from those at present 

 indicated by the ordinary chemical classification. 



