of simple alimentary substances, &c. 357 
of digestion, however, had for a long time occupied my 
particular attention ; and by degrees I had come to the 
conclusion, that the principal alimentary matters employed 
by man, and the more perfect animals, might be reduced to 
three great classes, namely, the saccharine, the oily, and the 
albuminous : hence, it was determined to investigate these in 
the first place, and their exact composition being ascertained, 
to inquire afterwards into the changes induced in them by 
the action of the stomach and other organs during the sub- 
sequent processes of assimilation. In conformity with this 
plan, the object of the present communication is the consi- 
deration of the first class or family above-mentioned, namely, 
the saccharine. 
Preliminary observations on the analysis of organised substances. 
Vegetable substances contain at least two elements, hy- 
drogen and carbon ; and most generally three, hydrogen, 
carbon, and oxygen. Animal substances are still more com- 
plicated ; and besides the above three, usually involve a 
fourth element, namely, azote, to which they appear to owe 
many of their peculiar properties. These general facts have 
been known ever since the elements themselves have been 
recognised as distinct principles, though the determination of 
the exact proportions in which they enter into any particu- 
lar substance, has always proved a most difficult problem. 
To enumerate all that has been done on this subject would 
be loss of time ; and it need only be mentioned, that all idea 
of separating the different elements from one another, so as 
to obtain them perse, has been long since abandoned, if indeed 
