142 ROTATION OF CROPS. 



pounds is so constant, that it would be difficult to trace a case of 

 more intimate connexion. It is extremely probable that th« 

 origin and formation of the organic constituents of the blood in 

 the organism of plants is closely connected with the presence of 

 phosphates. It must be supposed that the organic constituents of 

 the blood will not be formed in a condition adapted for their con- 

 version into blood, without the presence of alkalies and of phos- 

 phates, which are found constantly to accompany them ; and this 

 will be the case, even although carbonic acid, ammonia, and sul- 

 phates as a source of sulphur, be presented to them in the most 

 abundant quantity. But, even on the assumption that they could 

 be generated in the organism of the plant, without the action of 

 theso substances, we cannot suppose that they could be converted 

 into blood and flesh in the body of the animals, when the mineral 

 constituents of the blood were absent from the vegetable given 

 as food. 



But independently of these views, a rational farmer must en- 

 deavor to effect the purpose desired, and in doing so he must act 

 exactly as if the presence of the inorganic constituents of blood 

 (the alkalies and phosphates) were indispensable for the produc- 

 tion of the organic constituents ; for he must furnish to the plants 

 all the materials necessary for the formation of the stem, leaves, 

 and seeds. If he is desirous of making his land yield a maximum 

 of blood and flesh, he must furnish to it in abundant quantity 

 those constituents which the atmosphere cannot yield.* 



* When fresh arterial blood is evaporated to dryness- and incinerated, 

 ashes are obtained which yield to water salts of an alkaline reaction, but 

 not any alkaline carbonates, for no effervescence is occasioned by the addi 

 tion of an acid. These ashes consist of variable quantities of: — 



Phosphates of the alkalies, 



Phosphate of lime, 



Phosphate of magnesia, 



Basic perphosphate of iron 



Common salt, 



Sulphates of the alkalies. 

 The ashes of seeds contain : — 



BEANS 

 Peas, (vicia fab*). 

 Will. Buchner. 



13 \ «■» 



