416 FEEDING ANIMALS. 



only the nitrogenous and ash constituents of the food are 

 considered, as the carbonaceous elements are supplied by 

 the atmosphere. We must also have some basis for deter- 

 mining the proportion or amount of food elements to be 

 found in the manure. If there is no growth nor increase 

 in the live weight of the animal, and no rnilk produced, 

 then the amount of nitrogen and ash constituents passed 

 into the manure must be equal to these elements contained 

 in the food ; because the albuminoids and mineral elements 

 of the food used to build up the waste of the system, or for 

 the renovation of tissue, must be equal to these elements 

 broken down and passed off by the degradation of the 

 tissue; so that the same amount of valuable elements 

 contained in the food will be found in the manure. But 

 when the body is increasing in weight, or milk is produced, 

 then the albuminoids and mineral elements required to 

 form this increase of body or the milk, must be deducted 

 from these elements in the food consumed. A part of the 

 nitrogenous and mineral elements of the, food is left undi- 

 gested in passing through the alimentary canal, and this is 

 found in the solid excrement. What is digested of the 

 nitrogenous and ash constituents passes into the blood, and 

 is converted into animal increase, or milk, if the animal is 

 increasing in weight, or yielding milk, and the balance of 

 these constituents are separated from the blood by the 

 kidneys, and are passed in the form of urine. These 

 albuminoids are oxydized into urea before they are ex- 

 pelled from the system. Hippuric acid is also found in 

 the urine of herbivorous animals. 



We find the proportion of albuminoids that will appear 

 in the solid excrement by deducting the percentage of 

 digestible albuminoids from the whole amount. Dr. Wolff's 

 late experiments with sheep and other animals, show that 

 sheep digest of the various elements of certain foods as 

 given in the following table : 



