BUTTER. 289 



These compositions are by no means constant, but vary 

 considerably, being affected by the individual animal, 

 the breed, the food, and even by the management of the 

 dairy. This latter is important, because it shows how 

 bad or injudicious work in the dairy may affect the qual- 

 ity of the butter even in chemical composition, as will 

 be shown more fully further on. 



Margarine is not only a prevailing constituent of 

 butter, but it exists also in the fat of cattle and in olive 

 oil, and in human fat to a very large extent. Butter 

 is therefore a naturally excellent food for the human 

 race, containing as it does so large a proportion of one 

 of the materials — margarine — of which the human frame 

 is built up. This is white, hard, brittle, and its melting 

 point is 118 degrees. When pure it is unchangeable; but 

 when mixed with the various substances which exist in 

 butter — sugar, lactic acidj and caseine— it absorbs oxygen 

 from the atmosphere and changes into oleine, or one of 

 those odoriferous fatty acids which are present in ripened 

 butter to a small extent, but in old butter to a larger 

 extent, varying from one and a half to two per cent, and 

 potentially to an even greater degree as the provocative 

 impurities may be present. Just here might be men- 

 tioned, once more, the very great importance of the 

 preservation of the most perfect purity in every opera- 

 tion of the dairy; because every impurity in milk, cream, 

 butter, or cheese is an active ferment, producing either 

 inherent or internal decomposition or oxidation, by 

 which elements are changed in the most unexpected and 

 surprising manner. Thus by the absorption of a few 

 atoms of oxygen from the atmosphere margaric acid be- 

 comes changed into oleic acid and water ; the quality of 

 the butter being materially altered for the worse, the 

 firm, waxy texiure being lost and a soft, oily, greasy 

 character being assumed. And again, these solid and 

 fluid fats are also changed into the injurious acids which 



