NUTRITION. 61 



organized tissues of plants, that is, their cells, 

 fibres, vessels, &c. freed from their contents, are 

 composed of a substance which every where 

 possesses the same composition ; and that this 

 consists of 24 carbon, 20 hydrogen, and 10 oxy- 

 gen, without any nitrogen ;" ... " on the other 

 hand the substances into whose composition ni- 

 trogen enters, though very generally diffused 

 through the tissues of the plant, do not seem to 

 undergo organization, but to form part of the 

 contents of the cells, vessels, &c. of which these 

 tissues are composed. It is curious to remark 

 that precisely the reverse is the case with ani- 

 mals ; their tissues being composed of a sub- 

 stance containing nitrogen, and substances which 

 are destitute of it being never found in their 

 bodies in an organized state, but only existing 

 there in the cavities of their cells, tubes," &c. 

 (Veg. Physiology, p. 117, 163.) 



46. It is obvious from the nature of the nou- 

 rishment which plants require, that the condi- 

 tion of the soil in which they are grown is a 

 matter of great importance. This subject has 

 already been noticed in the " Introduction to 

 Organic Chemistry," which forms the fourth 

 Number of these " Small Books," 27, &c. 

 There is scarcely perhaps a stronger proof in 



