CHEMICAL SYNTHESIS 11 



ing down complex into simpler molecules, which the chemist cannot 

 imitate at present by laboratory methods. In other cases, again, the 

 chemist has discovered relationships in the laboratory which the living 

 organism has long been realising in the vital laboratory. It must be 

 left to the judgement of physiological chemists to decide whether in 

 the case of any particular relationship herein recorded the chemical 

 mechanism of the transformation is similar in the organism and in the 

 laboratory whether there is any analogy between the processes or 

 whether absolute ignorance must be declared. The consideration of 

 such problems cannot but give an impetus to further inquiry into the 

 chemical activities of animals and plants. 



Certain details of treatment which follow from the foregoing con- 

 siderations may now be dealt with. While following the main divi- 

 sions, such as hydrocarbons, alcohols, aldehydes, ketones, &c., under 

 which organic compounds are generally grouped, the information 

 which from the present standpoint is considered of the greatest impor- 

 tance is the particular generator which serves as a starting-point in 

 each synthesis. Since the generators under the present scheme are for 

 the most part themselves vital products, the relationships which from 

 the biochemical point of view are of the greatest interest are thus 

 brought into prominence. It was hoped at the outset of this under- 

 taking that it would have been possible to keep to the systematic 

 classification of the generators in the order of the above main divisions, 

 but the rapid progress of discovery made interpolations and rearrange- 

 ments so frequently necessary that this plan was found to be impracti- 

 cable in the time available and it had to be abandoned. This departure 

 from what may be considered the logical sequence will not, however, 

 be found of any practical disadvantage in using the work. The 

 systematic sequence has been observed as far as possible, and the 

 synthetical processes have been arranged under lettered paragraphs 

 with the name of the generator printed in italics so as to catch the 

 eye at once in running down the page. Each synthetical product has 

 also a registration number, so that cross-references are easily found 

 when necessary, the registration numbers which serve for such refer- 

 ences being printed in thick type in square brackets. The system of 

 cross-references, although throwing some additional trouble on the 

 reader, has been unavoidable in view of the fact that many synthetical 

 products serve as generators for numbers of other products. The 

 repetition of the synthetical processes every time a synthesised com- 

 pound is mentioned would have added enormously to the labour of 

 compilation, and would moreover have increased the size of the book 

 to an inordinate extent. In order to facilitate reference the registra- 

 tion number of the compound and the initial letters of the paragraphs 

 containing the descriptions of the synthetical processes are also printed 

 at the top of each page. 



Among other consequences which follow from this biochemical 



