128 POWER OF THE CHEMIST OVER MATTER. 



know not how far. The discovery of a new agent, or of a new mode 

 of treatment, may enable him to accomplish what he has not as yet the 

 means or the skill to perform. 



2°. He has it in his power to form, actually to produce, some of the 

 organic or organized substances which occu in living plants. He can 

 form gum, and grape sugar, in any quantiry. Thus far he can imitate 

 and take the place of the living 'principle it ^elf 



Numerous other cases are known, in 'vhichhe displays a similar 

 power. By the action of nitric acid upon starch or sugar, [see Lecture 

 III., p. 47,] he can form oxalic acid, which, as has already been shown, 

 occurs very largely in the vegetable kingd )m. By the action of heat 

 upon citric acid, he can decompose it an 3 produce an acid which is 

 met with in the Wolfsbane (Aconitum napellus), and hence is called 

 aconitic acid.* Also by the action of sul phuric acid he can change 

 salicine and phlorizine — substances extracted respectively from the bark 

 of the willow and from that of the root of the apple tree — into a resinous 

 matter and grape sugar. So, of the compounds which are found in the 

 solids and fluids of animal bodies, there are some which he has also 

 succeeded in forming by the aid of his chemical art. • 



Elated by such achievements, some chemists appear willing to hope 

 that all nature is to be subjected to their dominion, and that they may 

 hereafter be able to rival the living principle in all its operations. It is 

 true that what we now know, and can accomplish, are but the begin- 

 nings of what we may fairly expect hereafter to effect. But it is of con- 

 sequence to bear in mind the true position in which we now stand, and 

 the tBue direction in which all we at present know seems to indicate that 

 our future advances in knowledge, and in control over nature, are likely 

 to proceed. And this leads me to observe — 



3°. That our dominion is at present limited solely to transforming 

 and decomposing. We can transform woody fibre into gum or sugar— 

 we cannot form either gum or sugar by the direct union of their elements. 

 We can resolve salicine by the acid of sulphuric acid into resin and 

 grape sugar ; but we cannot cause the elements of which they consist to 

 unite together in our hands, so as to form any one of the three. We 

 cannot even cause the resin and the sugar to re-unite and rebuild the sali- 

 cine from which they were derived. 



So we can by heat drive off the elements of water from the citric and 

 cause the aconitic acid to appear ; but we cannot persuade the unwilling 

 compounds, when thus separated, to return to their former condition of 

 citric acid ; and, if we could, we should still be as far removed from the 

 power of commanding or compelling the direct union of carbon, hydro- 

 gen, and oxygen, in such proportions, and in such a way, as to build up 

 either of the two acids in question. 



Again, we can actually form oxalic acid by the action of nitric acid 



'These two acids differ from each other only iiy the elements of an atom of water. Thus 

 Citric Acid . . = C4 'i 04 

 Aconitic A;id . = C4 Hj O3 



Difference . . = Hi O or HO, one of water. 

 It is easy to see, therefore, how, by the evolution of the elements of an atom of water, the 

 one acid m::'' >>e changed into the other. The scientific reader will excuse me (if on the 

 grounds of simplicity alone) for representing, both here and in the text, the citric acid by 

 C Ha O4, instead of by Cia Hs On + 3HO, whic: Liebig and his pupils prefer. 



