MILK. 145 



it on the end of an old knife, then burn some casein curd or 

 cheese, and notice the strong ammonia smell from the latter. 

 If, now, we pour off the clean water from the curd, and carefully 

 evaporate the water in a saucer placed over the steam of a 

 kettle or in a slow oven, we shall get a white substance that 

 tastes sweet but gritty ; it is the sugar of the milk, called milk- 

 sugar or lactose. Finally, if we carefully dry out a little dish 

 of milk and burn it thoroughly, we shall have left a small 

 quantity of ash or mineral matter. Milk, therefore, consists ot 

 water, having particles of butter-fat floating in it undissolved, 

 and having in solution casein and albumen, milk-sugar, and 

 ash. The composition may be stated as follows : 



Water, from 80 to 90 averaging 87.0 per cent. 



Fat, from 2 to 10 ........ . " 4.0 " 



Casein or cheesy substance .. " 3.0 " 



Albumen " 0.5 *' 



Sugar or lactose " 4.8 " 



Ash or mineral matter " 0.7 " 



A pitcher of warm water gives off vapor into the air, but a 

 pitcher of ice water will have vapor settle up its sides from the 

 air. So it is with milk. Milk is warm when first milked and 

 we can smell the odor, the cow odor, as it passes off into the 

 air ; but it soon begins to cool down and vapors of the air 

 will settle upon its surface as upon the cold pitcher. If, there- 

 fore, we leave a pail of milk standing in the stable, or near any 

 food that has a bad smell, it will take up foul air that can after- 

 wards be tasted in the milk, the butter and the cheese. As 

 soon as milking is done the milk should at once be taken to 

 a clean milk-house or cellar. But bad odors and tastes can be 

 given from the food. Thus turnips, bad ensilage, cabbage, 

 rape and weeds of many kinds will affect the milk. All such 

 should be kept from the animal. Here we see a strong argu- 

 ment for keeping pastures clean. Every trace of musty food 

 such as mouldy ensilage or rotting roots should be kept from 



