PART I. 



DIYISIOISr I. 



THE PROXIMATE CONSTITUENTS OF PLANTS AND 

 VEGETABLE SUBSTANCES AS FAR AS HITHERTO 

 KNOWN; THEIR PROPERTIES; THEIR MODE OF 

 PREPARATION AND QUANTITATIVE ESTIMATION. 



My original intention was to bring this work into a kind of 

 systematic form — into a number of natural groups ; but I relin- 

 quished this purpose on account of very many gi-eat difficulties. 

 A very large number of the vegetable substances, treated on in 

 the following pages, are as yet so imperfectly investigated, that it 

 is impossible to determine their real constitution; consequently 

 they could not have been brought into any system at all. More- 

 over, not a few of the better-known substances have properties 

 which leave it doubtful to which of the groups they belong. For 

 instance, there are many dyeing substances, which possess all the 

 properties of resins or acids, and therefore can be placed just as 

 well among the resins as among the acids, and had to be looked 

 for sometimes amongst the resins, sometimes amongst the dyeing 

 substances, and sometimes amongst the acids. A sjoecial index 

 might have alleviated this difficulty; still, the system would not 

 have been better for all that. I preferred, in order to follow out the 

 practical object, to bring all the names into one alphabetical order; 

 and to facilitate consultation by tables of synonymes. 



The nature of a substance will be taught by its description. A 

 thorough investigation is wanting for a satisfactory result, and 

 herein lies an invitation to fill out gaps, and sometimes very con- 

 siderable ones, in our knowledge of vegetable compounds hithei-to 

 considered peculiar. Whoever devotes, his time to the solution 

 of such problems deserves more praise, I firmly believe, than he 

 who engages in the examination of vegetables not analysed before. 



