TRUE rnOSPECTS OF CHEMICAL SCIENCE. 129 



upon starch, or wood, or sugar, or any other of a great variety of vegeta- 

 ble substances — but we cannot prepare it by the direct union of its ele- 

 ments. We can only as yet procure it from substances which have 

 already been organized — which have been themselves produced by the 

 agency of the living principle. 



The same remarks apply with slight alteration to those substances of 

 animal origin to which I have above alluded as being within the power 

 of the chemist to produce at will. There is hardly an exception to the 

 rule, that in producing organic substances, as they are called, the chem- 

 ist must employ other organic substances which are as yet beyond his 

 art — which, so far as we know, can only be formed under the direction 

 of the living principle. Thus the sum of the chemist's power in imita- 

 ting organic nature consists, at present, in his ability — 



1°. To transform one substance found only in the organic kingdom 

 into some other substances, produced more or less abundantly in the 

 same kingdom of nature. This power he exercises when he converts 

 starch into sugar, or fibrin into albumen or casein. 



2°. To resolve a more complex or compound substance into two or 

 more which are less so, and of which less complex substances some may 

 be known to occur in vegetable or animal bodies. 



3°. To decompose organic compounds by means of his chemical agents, 

 and as the result of such decompositions to arrive at one or more com- 

 pounds, such as are formed under the direction of the living principle. 



In no one case can he form the substances of which animals and plants 

 chiefly consist, out of those on which animals and plants chiefly live. 



But this is the common and every-day result of the agency of the liv- 

 ing principle. Is there as yet, then, any hope that the chemical labo- 

 ratory shall supersede the vascular system of animals and plants ; or 

 that the skill of the chemist who guides tlie operations within it, shall 

 ever rival that of the principle of life which presides over the chemical 

 changes that take place in animal and vegetable bodies ? 



The true place, therefore, of human skill — the true prospects of chem- 

 ical science — are pointed out by these considerations. No science has 

 accumulated so many and such various treasures as chemistry has done 

 during the last 20 years — none is at present so widely extending the 

 bounds of our knowledge at this moment as the branch of organic chem- 

 istry — men may therefore be excused for entertaining more sanguine 

 expectations from the progress of a favourite science than sober reason- 

 ing would warrant. Yet it is of importance, I think, and especially in 

 a moral point of view, that amid all our ardour, we should entertain 

 clear and just notions of the kind and extent of knowledge to which we 

 are likely to attain, and — as knowledge in chemistry is really power 

 over matter — to what extent this power is likely ever to be carried. 



At present, if we judge from our actual knowledge, and not from our 

 hopes — there is no prospect of our ever being able to imitate or rival 

 living nature in actually compounding from their elements her nume- 

 rous and varied productions. That we may clearly understand, and be 

 able to explain many of her operations, and even to aid her in effecting 

 them, is no way inconsistent with an inability to imitate her by the re- 

 sources of art. This will, I trust, appear more distinctly in the sQbse- 

 quent lecture. 



