6 INTRODUCTORY 



that orcinol or a derivative would have to be as it were built into the 

 structure of the molecule. This phenol, which has of course been 

 completely synthesised, has therefore been included among the vital 

 products, and it is not at all improbable in view of the facility with 

 which some of the lichen acids furnish the compound by chemical 

 treatment and even by bacterial action that it may yet be found in 

 the vegetable kingdom. 



Resorcinol [70] presents a similar case, only the evidence that the 

 complex is contained in vital products such as paeonol [133], euxan- 

 thone [136], &c., has been in the first place obtained by the more 

 violent method of fusing with alkali. It is hardly likely that this 

 phenol will be ever found in the free state in plants, but it must 

 nevertheless be regarded as a vital product, since it has been proved by 

 synthesis as well as by the action of heated alkali that resorcinol is one 

 of the generators of both pseonol and euxanthone. 



For similar reasons the pyrogallol [84] complex is regarded as 

 being present in gallic acid, &c., the phloroglucinol [86] complex in 

 many colouring-matters of the pyrone group, and so forth. Another 

 instructive example is furnished by hydrojuglone [90] from the 

 walnut, Juglans regia. This compound is known to be a derivative 

 of naphthalene, and as it contains the naphthalene complex the 

 syntheses of this hydrocarbon are given in connexion with the phenol. 

 While these pages were undergoing final revision it was announced 

 by v. Soden and Rojahn (Pharm. Zeit. 47, 779) that the hydrocarbon 

 itself had been found in certain vegetable ethereal oils. 



III. 



The general tendency of the present work is to bring Carbon 

 Chemistry back to the point from which it departed three-quarters 

 of a century ago, when the leading discovery of the synthesis of urea 

 by Wohler showed that organic compounds could be formed without 

 vital intervention. Without desiring to reopen the question of the 

 existence of a special ' vital force,' it may be well to call the attention 

 of those physiologists who appeal to the achievements of synthetical 

 chemistry as conclusive evidence against the existence of such a force 

 to the fact so distinctly brought out by the summary of experimental 

 results herein recorded that the testimony of pure chemistry cannot, 

 as it at present stands, be legitimately interpreted into a direct nega- 

 tion of Vitalism in any form. This negation may, and probably will, 

 be made possible in the future when our chemical methods have been 

 made to approximate more closely to the vital methods. 



In the meantime it must not be forgotten that there is at present 

 but little reason for believing that our laboratory methods have much 

 analogy with the processes which go on in the living organism. All 



