MAMTTBES, 



without being materially changed. Its nature is 

 easily understood. It contains organic and mineral 

 mutters in nearly the condition in which they existed 

 in the hay. They have been rendered finer and softer, 

 but their chemical character (their composition) is not 

 materially altered. The dung also contains small 

 quantities of nitrogenous matter, which has leaked 

 out, as it were, from the stomach and intestines. 

 The digested food, however, undergoes further 

 changes which aifect its character, and it escapes 

 from the body in three ways i. <?., through the 

 lungs and skin, through the bladder, and through 

 tlm bowels. It will be recollected from the first 

 section of this book, p. 20, that the carbon in the 

 blood of animals unites with the oxygen of the air 

 drawn into the lungs, and is thrown off in the 

 breath as carbonic acid. The hydrogen and oxygen 

 unite to form a part of the water which constitutes 

 the moisture of the breath. 



That portion of the atmospheric part of the hay 

 which has been taken up by the blood of the ox, and 

 which does not contain nitrogen, is emitted through 

 the lungs. It consists, as will be recollected, of car- 

 bon, hydrogen, and oxygen, and these assume, in res- 

 piration, the form of carbonic acid and water. 



The atmospheric matter of the digested hay, in 

 the blood, which does contain nitrogen, goes to the 



* O / c5 



bladder, where it assumes the form of urea a consti- 

 tuent of urine or liquid manure. 



We have now disposed of the imperfectly digested 

 food (the dung), and of the atmospheric matter which 



