AGRICULTURAL EXPERIMENT STATION. 35 



DIGESTION EXPERIMENTS. 



THE INFLUEXCE OF FOOD COMBIXATIOXS UPON 

 DIGESTIBIEITV. 



W. H. JOKDAN. 



A large amount of time has been expended in determining the 

 digestibility of our various cattle foods, and the figures obtained 

 are known as coefficients of digestibility. These coefficients are 

 arranged in tables convenient for reference, and are much used in 

 a practical way for the calculation of rations. In practice it is 

 assumed that when the several materials in the ration are multiplied 

 by their respective percentages of digestibility, the sum of the 

 quantities thus obtained will represent very nearly the total digesti- 

 ble material fed ; in other words, it is assumed that no matter how 

 foods are combined, each food continues to have its peculiar rate 

 of digestibility, which is not changed to any important extent by 

 the influence of the foods which accompany it. 



The correctness of the position is somewhat questioned by those 

 familiar with related facts, their doubt being based not so much 

 upon theoretical reasons as upon the apparent outcome of certain 

 digestion experiments. 



The digestibility of a food in a particular instance must be 

 determined by two factors : 



(1) What has been termed the "inherent resistance" of the 

 food to the solvent action of the digestible liquids. 



(2) The supply in abundance of these digestive fluids. 



The writer has always inclined to the view that the first factor is 

 so largely the controlling one that unless the animal is under 

 abnormal conditions it almost wholly determines the amount of the 

 food that shall pass into solution. To illustrate, egg albumen is 

 wholly peptonized by the gastric juice, or starch is wholly inverted 

 to glucose under the action of the pancreatic juice, and these results 

 will always obtain when these two juices are secreted in proper 

 abundance, not being influenced by the relative amounts present of 

 other compounds that are to be digested. There is a possibility 

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