DIGESTIBILITY OF FEEDING SUBSTANCES. 231 



Rational Mode of Feeding Ruminants," beginning with 1860, 

 have acquired a particular historical interest on account of 

 their clear demonstration, to the thinking agriculturist, that 

 a rational and economical mode of feeding our domesticated 

 animals cannot be secured without a due consideration of 

 the chemical and physiological conditions of both fodder and 

 animal involved. The results of these experiments were 

 not of less importance to the practical farmer, whose first 

 interest, quite naturally, centred in the financial side of the 

 operation ; for it was shown, that, with the best modes 

 known to determine the actual effect of fodder on the weight 

 of the animal, the identical effect had been produced with 

 five different kinds of fodder substances, at a difference in 

 the daily expenses for fodder of from thirty-nine to forty- 

 four per cent. The most expensive diet used had been 19.5 

 pounds of clover-hay (9.4 cents) per day for one thousand 

 pounds of live-weight (cost of clover-hay in this case from 

 nine dollars and a half to ten dollars per ton). 



The growing evidence that a mere knowledge of the chemi- 

 cal composition of the fodder substances alone did not suffice 

 to determine their exact absolute feeding value, and that the 

 degree of their digestibility does exert a controlling influ- 

 ence on their qualification to support animal life, rendered it 

 desirable, in the interest of a safer rule for farm-practice, to 

 institute a detailed examination in that direction. 



Dr. Grouven, chemist to the Experiment Station, Salz- 

 miinde, Germany, entered, at this stage of the progressive 

 movement, upon a series of experiments (1860 to 1864) 

 which have fairly revolutionized the science of stock-feeding, 

 and have furnished, in common with such modifications as 

 the progress in more detailed investigations has since ad- 

 vised, the basis of our present ruling modes of feeding farm- 

 stock. He began with a critical compilation of the best 

 previously conducted feeding experiments, and collected the 

 most reliable analytical material concerning fodder sub- 

 stances, adding largely from his own laboratory observations. 

 He conducted personally a series of elaborate feeding ex- 

 periments, and tested not only the feeding-value of com- 

 pound fodder substances, but studied also the effect of the 

 isolated plant-constituent, as fat, starch, cane-sugar, grape- 

 sugar, wax, and resinous substances, cellular matter, dextrine, 



