THE INFLUENCE OF CFIEMISTRY. 103 



series of oro^anic compounds, which begin with the inorganic 

 articles of plant food, to the most complicated constituents 

 of the brain of the animal, we cannot notice a break nor an 

 interruption. The constituent of the animal food, which 

 produces the principal part of its blood, is the product of 

 the vital activity of the plant." 



Having attempted in preceding pages to show the impor- 

 tant influence which chemistry has exerted on the develop- 

 ment of a more concise idea of what constitutes a complete 

 article of animal diet, from a physiological standpoint, i. e., 

 regarding its special fitness to sustain the life of animals, I 

 propose to point out briefly the effect which the above-stated 

 information has had on the rational agricultural practice of 

 to-day. 



The recognition of the physiological fact, that no single 

 constituent of a plant can support animal life for any 

 length of time, — neither nitrogenous matter, nor fat, sugar 

 or starch, nor mineral matter ; but that certain proportions 

 are required of each of the three principal groups of sub- 

 stances previously described, induced chemists to study more 

 closely the various farm plants with particular reference to 

 the relative proportion, and to the special quality of their 

 proximate constituents. 



The results obtained in this connection soon revealed the 

 fact, that not two kinds of plants, or even parts of plants, 

 are of an identical composition. It became soon a[)parent 

 that the composition of one and the same plant even dillers 

 widely not only at the various stages of growth and matu- 

 rity, but also when raised in a ditferent climate and upon a 

 diflerent kind of soil, as well as in case of a varying system 

 of manuring and of cultivation. Whilst it could not be 

 denied that the character and the quality of each farm plant 

 became soon much better known, and that actual fet'dino^ 

 experiments carried on with a due consideration of a more 

 exact chemical examination of the particular kind of fodder 

 consumed, had aflbrded a safer basis for Hnal couclusious, it 

 became not less evident, in the course of time, that the chem- 

 ical analysis of an article of fodder alone did not sutlice to 

 decide the comparative feeding value of diflerent kinds of 

 farm plants, or even of the same plants in diflerent stages of 



