Sept. 1 6, 1880] 



NATURE 



473 



meteorological influences affecting the culture of the vine. In 

 1838 he published the results of an elaborate research on the 

 principles underlying the value of a rotation of crops. He 

 determined by analysis the composition, both organic and in- 

 organic, of the manures ajiplied to the land, and of the crops 

 harvested. In his treatment of the subject he evinced a clear 

 perception of the most important problems involved in such an 

 inquiry ; some of which, with the united labours of himself and 

 many other workers, have scarcely yet received an undisputed 

 solution. 



Thus, in the same year (iSjS), he published the results of an 

 investigation on the question \vhether plants assimilate the free 

 or uncombined nitrogen of the atmosphere ; and although the 

 analytical methods of the day were inadequate to the decisive 

 settlement of the point, his conclusions were in the main those 

 which much subsequent work of his own, and much of others 

 also, has served to confirm. 



The foregoing brief historical sketch is sufficient to indicate, 

 though but in broad outline, the range of existing knowledge on 

 the subject of agi-icultural chemistry prior to the appearance of 

 Liebig's memorable work in 1S40. It will be seen that some 

 very important and indeed fundamental facts had already been 

 established in regard to vegetation, and that Eoussingault had 

 not only extended inquiry on that subject, but he had brought 

 his own and previous results to bear upon the elucidation of long 

 recognised agricultural practices. There can be no doubt that 

 the data supplied by his researches contributed important 

 elements to the basis of establislied facts upon which Liebig 

 founded his brilliant generalisations. Accordingly, in 1841, 

 Dumas and Boussingault published jointly an essay which after- 

 wards appeared in English under the title of "The Chemical 

 and Physiological Balance of Organic Nature; "and in 1S43 

 Boussingault published a larger work, which embodied the 

 results of many of his own previous original investigations. 



The appearance of Liebig's two works, which were contribu- 

 tions made in answer to a request submitted to him by the 

 committee of this Section of the British Association, constitute a 

 veiy marked epoch in the history of the progress of agricultural 

 chemistiy. In the treatment of his subiect he not only called to 

 his aid the previously existing knowledge directly bearing upon 

 it, but he also turned to good account the more recent triumphs 

 of organic chemistry, many of which had been won in his own 

 laboratory. Further, a marked feature of his expositions was the 

 adoption of what may be called the statistical method — I use the 

 word statistical rather than quantitative, as the latter expression 

 has its own technical meaning among chemists, which is not 

 precisely what I wish to convey. 



The discussion of the processes of fermentation, decay, and 

 putrefaction, and that of poisons, contagions, and miasms, con- 

 stituted a remarkable and important part of Liebig's first report. 

 It was the portion relating to poisons, contagions, and miasms, 

 that he presented to this Section as an instalment, at the meeting 

 of the Association held at Glasgow in 1840. It was in the 

 chapters relating to the several subjects here enumerated that he 

 developed so prominently his views on the influence of contact 

 in inducing chemical changes. He cited many known transfor- 

 mations, other than those coming under either of the heads in 

 question, in illustration of his subject ; and he discussed with 

 great clearness the different conditions occurring, and the dif- 

 ferent results obtained, in various processes — such as the different 

 modes of fermenting beer, the fermentation of wine from dif- 

 ferent kinds of grapes, the production of acetic acid, iS;c. As 

 is well known, he claimed a purely chemical explanation for the 

 phenomena involved in fermentation. He further maintained 

 that the action of contagions w as precisely similar. In his latest 

 writings on the subject (in 1S70) he admits some change of view; 

 but it is by no means easy to decide exactly how much or how 

 little of modification he would wish to imply. 



Liebig's second report, presented at the meeting of this Asso- 

 ciation in 1842, .and pubhshed under the title of " Animal 

 Chemistry, or Organic Chemistry in its Applications to Physio- 

 logy and Pathology," perhaps excited even more attention than 

 his first ; and, probably from the manner as much as from the 

 matter, aroused a great deal of controversy, especially among 

 physiologists and physicians. Liebig was severe upon what he 

 considered to be a too exclusive attention to morphological 

 characters in physiological research, and at any rate too little 

 attention to chemical phenomena, and, so far as these were 

 investigated, an inadequate treatment of the subject according to 

 strictly quantitative methods. 



Omitting the fat which the carnivora might receive in the 

 animals they consumed, he stated the characteristic difference 

 between the food of carnivora and herbivora to be, that the 

 former obtained the main proportion of their respiratoi-y mate- 

 rial from the waste of tissue ; whilst the latter obtained a large 

 amount from starch, sugar, &c. These different conditions of 

 life accounted for the comparative leanness of carnivora and 

 fatness of herbivora. 



He maintained that the vegetable food consumed by herbivora 

 did not contain anything like the amount of fat which they 

 stored up in their bodies ; and he showed how nearly the com- 

 position of fat was obtained by the simple elimination of so 

 much oxygen, or of oxygen and a little carbonic acid, from the 

 various carbohydrates. Much less oxygen would be required to 

 be eliminated from a quantity of fibrine, &c., containing a given 

 amount of carbon, than from a quantity of carbohydrates con- 

 taining an equal amount of carbon. The formation of fatty 

 matter in plants was of the same kind ; it was the result of a 

 secondary action, starch being first formed from carbonic acid 

 and water. 



He concluded from the facts adduced that the food of man 

 might be divided into the nitrogcnised and the tion-nitrogenised 

 elements. The former were capable of conversion into blood, the 

 latter incapable of such transformation. The former might be 

 called the plastic elements of nutrition, the latter elements of 

 respiration. From the plastic elements, the membranes and 

 cellular tissue, the nerves and brain, cartilage, and the organic 

 part of bones, could be formed ; but the plastic substance must 

 be received ready-made. Whilst gelatine or chondrine was 

 derived from fibrine or albumen, fibrine or albumen could not 

 be [reproduced from gelatine or chondrine. The gelatinous 

 tissues suffer progressive alteration under the influence of oxygen, 

 and the materials for their re-formation must be restored from 

 the blood. It might however be a question whether gelatine 

 talcen in food might not again be converted into cellular tissue, 

 membrane, and cartilage, in the body. 



Apparently influenced by the physiological considerations 

 which have been adduced, and notwithstanding in some passages 

 he seemed to recognise a connection between the total quantity 

 of oxygen inspired and consumed and the quantity of mechanical 

 force developed, Liebig nevertheless very prominently insisted 

 that the amount of muscular tissue transfoi-med — the amount of 

 nitrogenous substance oxidated — was the measure of the force 

 generated. He accordingly distinctly draws the conclusion that 

 the requirement for the azotised constituents of food will be 

 increased in proportion to the increase in the amount of force 

 expended. 



It will be obvious that the question whether in the feeding of 

 animals for the exercise of mechanical force, that is, for their 

 labour, the demands of the system will be proportionally the 

 greater for an increased supply of the nitrogenous or of the non- 

 nitrogenous constituents of food, is one of considerable interest 

 and practical importance. To this point I shall have to refer 

 further on. 



So far, I have endeavoured to convey some idea of the slate of 

 knowledge on the subject of the chemistry of agriculture prior to 

 the appearance of Liebig's first two works bearing upon it, and 

 also briefly to summarise the views he then enunciated in regard 

 to some points of chief importance. Let us next try to ascertain 

 something of the influence of his teaching. 



Confining attention to agricultural research, it maybe observed 

 that about the year 1S43, that is very soon after the appearance 

 of the works in question, there was established the Chemico- 

 Agricultural Society of Scotland, which was, I believe, broken 

 up, after it had existed about five years, because its able chemist, 

 the late Prof. Johnston, was unable to find a remedy for the 

 potato disease. Shortly after this, the Highland and Agricultural 

 Society of Scotland appointed a consulting (chemist ; somewhat 

 later the Royal Agricultural Society of England did the same ; 

 and later still followed the Chemico-Agricultural^ Society of 

 Ulster. Lastly, the very numerous " Agricultural Experimental 

 Stations " which have been established, not only in Germany, 

 but in most Continental States, owe their origin directly to the 

 writings, the teachings, and the influence of Liebig. The move- 

 ment ?eem5 to have originated in Saxony, where Stockhardt had 

 already stimulated interest in the subject by his lectures and his 

 writings. After some correspondence, in 1S50-51, between the 

 late Dr. Crucius and others on the one side, and the Government 

 on the other, the first so-called "Agricultural Experimental Sta- 



