IMPORTANCE OF ALKALIES. 141 



the nutritive parts of plants must contain all the constituents of 

 the blood, and not merely one or two of them. 



It cannot be supposed that blood will be formed in the body of 

 an animal, or milk in that of a cow, if their food fail in even-ono 

 of the constituents necessary for the sustenance of the vital func- 

 tions. The compounds containing nitrogen and sulphur, as well 

 as the alkalies and phosphates, are constituents of the blood ; but 

 the conversion of the former into blood cannot be conceived with- 

 out the presence and co-operation of the latter. 



According to this view, the power of any part of a plant to 

 support the life of an animal, and to increase its blood and flesh, 

 is in exact proportion to its amount of the organic constituents of 

 the blood, and of the materials necessary for their conversion into 

 blood — viz., of alkalies, phosphates, and ehlorides (common salt 

 or chloride of potassium). 



It is highly worthy of observation, and of great significance to 

 agriculture, that the vegetable compounds containing sulphur and 

 nitrogen, which we have designated as the organic constituents 

 of the blood, are always accompanied, in the parts of the plants 

 where they occur, with alkalies and with phosphates. The juice 

 of potatoes and of beet contains vegetable albumen accompanied 

 by salts of alkaline bases, and by soluble phosphate of magnesia ; 

 in the seeds of cereals and of peas, beans, and lentils, there are 

 alkaline phosphates and earthy salts. 



The seeds and fruits, which are richest in the organic con- 

 stituents of the blood, contain also the inorganic, such as the phos- 

 phates, in large quantity ; other parts of plants, as the potatoe, and 

 the various roots, which are proportionally so poor in the former 

 ingredients, contain a much smaller quantity of the latter. 



The contemporaneous occurrence of both these classes of com- 



and acetic acids. Anhydrous acetic acid contains carbon and the constitu- 

 ents of water, in exactly the same relative proportions as woody fibre (Pe- 

 ligot), which also yields acetic acid under similar circumstances. 



These methods of decomposition have induced a distinguished French 

 chemist to assume the existence of ready-formed oxalic acid in tartaric 

 acid ; certainly its elements are present, besides those of a second body, 

 which, like sugar, gum, and woody fibre, may be viewed as a compound 

 of carbon with water. 



