and the physician no longer expects that he can 

 feed a child, without disastrous consequences, 

 on mere starch or arrow-root. The fact is now 

 established, that land without the elements of 

 fertility, must have theui given to it, before it 

 can be fertile ; and that to form nerve or muscle 

 in the body, food containing their elements must 

 be taken. 



If it be said that to the study of physiology a 

 knowledge of the composition of organic bodies 

 was an important preparation, it may also be 

 added that a knowledge of the elementary com- 

 position of bodies was much more easily ob- 

 tained by the facilities of analysis introduced by 

 Liebig. 



Many persons may have seen attached to one 

 of his best portraits, which was lithographed at 

 Frankfort five yeai's ago, a small crooked-look- 

 ing apparaus on one side of him, in which five 

 globes witii white spots on them are the princi- 

 pal things seen : this is the potash apparatus, a 

 series of bulbs in which caustic potash is put to 

 collect the carbonic acid passing from the de- 

 composing organic matter undergoing analysis. 

 It is scarcely right to connect his name in such 

 a marked manner with an invention so much 

 inferior to his many other labors, but that also 

 speaks a truth not to be forgotten easily, and 

 makes us believe that the gratitude of one who 

 had labored vrirh little profit at less elegant ap- 

 paratus had oiFered this to him, although on an 

 unlucky part of fhe sacred niche. 



As a life spent like that of Professor Liebig 

 can offer little for the writer, unless what is ei- 

 ther directly or indirectly connected with sci- 

 ence, it will be better for us to look over that 

 which he has done, and to give the true reasons 

 of the great name he has acquired. 



The chemical section of the British Associa- 

 tion desired him to prepare a report on the state 

 of organic chemistry. If we look at the work 

 which resulted, well known under the title of 

 " Chemistry in its applications to Agriculture 

 and Physiology," we perceive, that in consider- 

 ing the state of organic chemistry, and collecting 

 the information on die various branches it in- 

 cludes, he was led to generalize ; and by em- 

 bracing many phenomena as he did in a few 

 simple ideas, he has given us a resting-place 

 hitherto unforseen ; and although the vanguard 

 only may have an-ived in quarters, and room be 

 not ready for every arrival, it is no more than 

 we must always expect, as another march must 

 sooner or later be made. •' He has endeavored 

 to develop in a manner corresponding to the 

 present state of science, the fundamental princi- 

 ples of chemisti-j' in general, and the laws of or- 

 ganic chemistry in particular, in their applica- 

 tions to Agriculture and Physiology, to the 

 causes of fermentation, decay, and putrefaction, 

 to the vinous and acetous fermentations, and to 

 nitrification. The conversion of woody fibre 

 into wood and mineral coal, the nature of poi- 

 son.?, contagions, and miasmas, and the causes of 

 their action on the living organism, have been 

 elucidated in their chemical relations." 



This is somewhat more than the association 

 expected of him, an analysis of the existing the- 

 ories and facts would have satisfied tliem. 



It may be useful to repeat some of the more 

 striking parts of it : — 



Plants are formed of carbon, hydrogen, oxy- 

 gen and nitrogen, phosphorus, sulphur, and sev- 

 eral metallic oxides, such as those that occur in 

 soil. Carbon and hydrogen are never absent 

 from plants — they are found in every portion of 

 i3T: 



the plant, and increase togetlier ; oxygen is pre- 

 sent almost as generally, and constitutes a large 

 portion of the fibre of wood, and of the nutritive 

 portion of the piaut. The oxygen contained in 

 woody fibre, sugar, gum, and starch, that is in 

 the much larger portion of tlie vegetable world, 

 is in the same proportion to tlie hydrogen con- 

 tained, as in walor ; that is to say, if we take 

 the hydrogen and oxygen from them, the com- 

 pound obtained wiU be simply water, and car- 

 bon will be left ; tliey may then be said to be 

 compounds of carbon with water, although there 

 are many objections to viewing them in this 

 light. Nitrogen is a constituent of all gluten, 

 albumen, and casein, substances cs.sential to our 

 food ; along with it sulphur and phosphorus are 

 always found, and several metallic oxides, such 

 as lime, magnesia, iron oxide, soda, and potash, 

 are never absent Whence do all these sub- 

 stances come, may now be asked ? First, the 

 carbon : it w^as long supposed to be given to the 

 plant by means of humus; humic acid, or ulmic 

 acid, a known matter to be seen in mould, and 

 to be obtained in large quantities from decayed 

 woods, and other vegetable matter. Rich mould 

 was generally seen to contain a great deal of 

 this ; and it was supposed that the plants im- 

 bibed it merely, and digested it : that this could 

 not possibly be the case, is .shown from its almost 

 insolubility in water. 



Humus has been analyzed by various persons 

 — none, however, have come to certain results; 

 the differences amount to as much as twenty 

 per cent, of carbon; but they all agree in giving 

 it a large portion. We can form it artificially in 

 various ways; that is, by various decomjiosi- 

 tions of organic matter, by treating woody fibre 

 with alkalies, or sugar and starch with acids. — 

 It is organic matter approaching an inorganic 

 state, and in which we may consider vegetable 

 life to be entirely extinct. Vegetables, when 

 they die, undergo decomposition ; by means of 

 the oxygen of the air they are gradually burnt, 

 the carbon unites witli the oxygen, the hydro-i 

 gen and oxygen assume the usual form in which 

 they exist, uncombined with carbon, viz : wa- 

 ter; and as this takes place, the remaining mass 

 approaches more and more an miorganizcd 

 charcoal merely. Such a condition is highly fa- 

 vorable to its farther union with oxygen, the 

 bond which held it together, its vegetable life, 

 being now gone, it naturally returns to the state 

 in which only it can be useful to other plants, 

 viz : carbonic acid. It is a destruction of our 

 analogies to suppose that a vegetable can live 

 on the decayed matter of another ; the true po- 

 sition of the plant seems to be to form from the 

 mineral world organized matter. 



Glauber, an old chemist, if not alchemist, of 

 the seventeenth century, was the first to observe 

 that plants fed on any of the gases or earths. It 

 is remarkable that no one has attended to his 

 discoveries; he placed a plant in a jar of car- 

 bonic acid gas, and found, after a time, that the 

 gas had become oxygen. It is right that in men- 

 tioning the works of the present day. we should 

 not forget the labors of the past. The time will 

 come when two centuries will be a distance too 

 small to be regarded, and Glauber, Saussnre, 

 and Liebig, will be mentioned more as co-work- 

 ers, than as a series of w^orkers. The same 

 chemist also taneht the value of several mineral 

 salts in growing plants. But after the composi- 

 tion of carbonic acid was known, Saussure, Da- 

 yy. and others have shown that carbonic acid 

 is converted by plants into oxygen gas, a Buffi- 



