Liebig's Organic Chemistry applied to Agriculture. 557 



does not vary, we obtain for all the plants, 2,700,000 lbs., or 54,000 

 cubic feet of water. With this water an equal number of cubic feet, 

 or 5,625 lbs. of carbonic acid, are introduced into the plants, which 

 answers to about 1,500 lbs. of carbon. 



Though, from the nature of the subject, the facts on which these 

 two calculations are founded have no claim to great exactness, and 

 are only to be considered as a very rough estimate, yet they give a 

 result in which the difference is not very great ; and they prove at 

 least one thing, namely, — that the carbonic acid which enters plants 

 with water, by means of their roots, is completely sufficient to ex- 

 plain the source of carbon existing in the plants. When we consider, 

 moreover, the capacity of humus to absorb carbonic acid, we shall be 

 almost justified in assuming that the water which is absorbed by 

 roots is completely saturated with carbonic acid. 



I have now shown that Dr. Liebig has not at all understood the 

 problems of physiology, as far as he has touched upon them in this 

 chapter ; that he has not produced any new fact, with the exception 

 of the unfounded assertion that equal extents of soil produce equal 

 quantities of carbon; that he does not know, or pretends not to 

 know, that all the false theories on which he has stumbled, have been 

 invented by chemists, and have only been adopted from them by 

 physiologists, among whom, however, there always have been some 

 who have entertained more just views ; and lastly, that the only new 

 thing which he has introduced, appears, according to our present 

 knowledge, to be quite unfounded. It cannot, then, fail to excite 

 indignation, that Dr. Liebig should, at the end of the chapter, make 

 a violent attack upon physiologists, of whom, in his ignorance, 

 he has formed an idea, existing only in his own fancy, and on which 

 all his offensive language is grounded. It is rather unfortunate that 

 in a book dedicated to Alexander Von Humboldt, the author should 

 assert, that the most distinguished of our physiologists are un- 

 acquainted with the elements of chemistry, whilst that class of 

 natural philosophers with pride and truth enumerate among them 

 that great philosopher himself. 



Dr. Liebig reproaches vegetable physiologists with ignorance of 

 chemistry and physics, and says they are incapable of making experi- 

 ments. As to the first point, I shall use the words of Dr. Liebig 



