102 BOAED OF AGRICULTURE. 



constituents of the fodder should be properly supplemented^ 

 if necessary, to meet the special wants of the animal. 



The previous short sketch of Liebig's experimental inves- 

 tigations regarding the requirements of a complete animal 

 diet cannot fail to show that his demonstration of the neces- 

 sity to compound fodder rations with reference to three dis- 

 tinctly differing groups of plant constituents has given us a 

 more concise idea concerning the process of animal nutrition, 

 and thereby furnished us with a safer basis for studying the 

 feeding effect of our farm crops. 



The extensive practical chemical work which has furnished 

 him with the material for his conclusion regarding the 

 process of animal digestion, assimilation, respiration, etc., 

 and the dependency of the animal food on the constituents of 

 plants, is largely due to the careful scientific labors of many 

 other eminent scientists ; the comprehensive interpretation 

 of their results are essentially his own. 



Chemical physiology, as a distinct field of scientific research, 

 originated with Liebig ; yet it is equally true that some of 

 the first and of the most important chemical physiological in- 

 vestigations are due to distinguished pioneers in comparative 

 anatomy and modern physiology, — J. V. Miiller and others, 

 contemporaries of him. 



A characteristical statement of Liebio; reo'ardinof the rela- 

 tion which exists between the vegetable and the animal king- 

 dom may close this chapter. 



" A comprehensive law of nature connects the develop- 

 ment of the organs of an animal, its growth and its increase 

 in weight with the consumption of certain substances, which 

 are identical with the principal constituents of its blood ; it is 

 manifest that the animal organism produces its blood only as 

 far as its form is concerned ; and, also, that nature has denied 

 to it the power to produce it out of other substances, which 

 are not identical with the princij)al constituents of its blood. 



" The animal body is a higher organism, which begins its 

 development with those materials with which the life of the 

 ordinary fodder plant usually terminates. As soon as the 

 fodder crops and the grain crops have produced their seeds, 

 they die ; with the production of the fruit, a period of life 

 in the case of the perennial plant ends ; in the innumerable^ 



