MEMOIR OF LIEBIG. 



169 



cient proof that they have formed their structure 

 from it Saussure showed that the upper strata 

 of the air contained more carbonic acid than the 

 lower — a fact, the contrary of which is general- 

 ly believed : also, that by night there is more 

 carbonic acid in the atmosphere than by day. — 

 Now, plants in the absence of light, are incapa- 

 ble of converting the carbon of carbonic acid to 

 their own use, or at least in very small quanti- 

 ties, so that what they do absorb, or have ab- 

 sorbed, is given out at night unchanged. Of the 

 sources of oxygen and hydrogen in plants, not 

 much uced be said here. The fact of the de- 

 composition of water, in order to obtain a sur- 

 plus of hydrogen for certain compounds, such 

 as the oily, resinous, &c. seems beyond doubt, 

 and the presence of oxygen in the plant can be 

 accounted for in several ways. The assimila- 

 tion of both of these substances presents phe- 

 nomena very instructive ; but that of nitrogen 

 being somewhat more so. and having given rise 

 to the most original theories and extensive dis- 

 cussion, may with advantage be looked to for a 

 moment. It is -well known that Davy consid- 

 ered ammonia as of great importance in ma- 

 nures, and proposed plans for preserving it ; but 

 having given him his due, and not forgetting 

 our friend Glauber, who saw this thing as clear- 

 ly as any man could, unacquainted with modern 

 analysis, we must now give the rest of the pi-aise 

 to Professor Liebig, who showed that it is the 

 inorganic state into which azotized organic mat- 

 ter enters to render it capable of a set-ond organ- 

 ization ; and that whilst Nature uses the atmos- 

 phere as a reservoir of the decomposed, she like- 

 wise uses it as a reservoir of food for the com- 

 posing vegetables. 



If ammonia be the last product of the trans- 

 formation of azotized bodies, it is, of course, to 

 be looked for in the atiuosphere. As ammonia 

 is very soluble in water, it must be then washed 

 down by the rain ; and after a long drouth -we 

 may expect that the rain will wash down a con- 

 siderable quantity. The ammonia was looked 

 for by Professor Liebig in a shower of rain, and 

 it was found ; and it has even been obtained 

 with the peculiar smell of organic matter at- 

 tached to it. The quantity contained in the at- 

 mosphere has been estimated as one-quarter of 

 a grain in 1,132 cubic feet. In hot climates the 

 nitrogen is found combined with ox}'geu, so as 

 to form nitric acid ; since the full value of the ni- 

 trogen in these compounds has been seen, we 

 have had a change, not in the theory merely, 

 but in the \vhole practice of our farmers ; and 

 the trade occasioned by it has been sufficient to 

 employ some hundred vessels at a time, and 

 considerably to alter our ideas of the value of 

 many waste products in the aits. Its indirect 

 influence is no Ic-^s valuable, as the guano of 

 our own country, the waste matter of our own 

 towns, husbanded as it ought to be, will not on- 

 ly be sufficient to supply the farmer ^vhen the 

 foreign guano is spent, but the removal of it will 

 purify our streets and our streams, and in no 

 small measure add to our domestic comfort, and 

 our sanitary condition. 



The true valueof in organic matter, as manure, 

 is especially insisted on by Liebig: the neces- 

 sity for phosphates, sulphates, and silicates, has 

 been a guide in the management of the rotation 

 of crop.s, which will, when fuily followed out, 

 prevent much loss of time, and prevent any pity 

 being thrown away on poor land, w hich we say 

 is weary of such iiard labor. Hard labor can- 

 not be sustained witliont good food ; tliis we 

 (37:i) 



must give the ground, and food is never so ex- 

 pensive as to be unable to pay itself by increase 

 of strength. 



Phosphates and silicates are the most neces- 

 sary inorganic salts, v^'hich our soils in general 

 want ; sulphates are more easily procured in the 

 form of gypsum. We may obtain phosphates 

 by using bones, although a cheaper mode would 

 be desirable ; but silicates ai-e certainly a desid- 

 eratum, unless the professor has, in his present 

 new manures, got over the difficult3^ 



It will, of course, be often said, as it has, in- 

 deed, been said, that this is not new. It will be 

 useless to ask what is new, and what is not ; as 

 a .system— as a whole, the connection between 

 the vegetable and mineral kingdom has been 

 so cleverly given, so many facts before doubted 

 have not only been proved, but been shown to 

 be necessary, that no one can look on it with- 

 out admiring the artist, (if so we may term him,) 

 by whomsoever and wheresoever the materials 

 were collected ; or, to use his own simile, he 

 v^'ent into a cavera in which were a number of 

 loo.se bones — he collected them, and formed 

 thereby the perfect skeleton of a noble animal. 

 This may be said of a part of his work, and 

 it may be said without fear, the original mat- 

 ter which he has brought forward is sufficient 

 to make him careless as to small losses. 



The principles of nutrition, as illustrated by 

 him, are so beautiful, however unknown to ma- 

 ny, and understood by still fewer, that it will 

 not be out of place to give a short summary of 

 some points. We see daily coming from tlie 

 press such vigorous conti-adictions, in England 

 chiefly by unscientific men, and in America by 

 men at least pretending to science, that we 

 know they are little understood. The analysis 

 of albumen, casein, and gluten, are now kno'wn 

 to have been made in the most accurate manner 

 by Mulder, and others, and the composition of 

 muscle is so well known, that we cannot hesi- 

 tate in saying that the latter is formed from the 

 former. They all contain a lai'ge proportion of 

 nitrogen — no flesh can exist without nitrogen — 

 be it the flesh of man or of beast, of fish or of 

 fowl, nitrogen exists in it and in tlie same pro- 

 portions. Now all our food must have nitrogen 

 in it, else how could our flesh have it ? We are 

 continually giving out nitrogen fi-om our bodies, 

 and how can it be supplied again, but by a re- 

 newal of it in our food ? Itisaquestion too simple 

 to require a lengthened explanation, now that 

 the way is prepared for us, and the objections to 

 it too trivial to require answering. In fact, it is 

 no\v as well established as that food is at all 

 necessary for us. No animal c;m feed on sugar, 

 and live ; can feed on starch or gum, and yet 

 continue strong ; these substances contain no 

 flesh — they contain no albumen, which is the 

 same thing. If a man says that he lives on su- 

 gar and water only, are we to believe him ? cer- 

 tainly not. If he says that he becomes fat by 

 eating sugar, we may believe him. because the 

 ekmonts of fat are found in sugar : but at the 

 same time to support the other functions of tlie 

 body, albumen, or a similar compound, must be 

 taken along with it. Arrowroot, or starch, is 

 sometimes taken, or rather was once taken, to 

 support strength ; but there is no readier mode 

 of destroying strength than by giving for food a 

 substance wrhich does not contain tlie es.sential 

 elements of muscle and of nerve, the organs with- 

 out which strength cannot exi.^t. True, children 

 have been kno\\'n to increase immensely in bulk 

 by eating arrowroot only, but tliey have been 



