64 MILK [vi 



bitter taste, and by its becoming liable to fermentative 

 curdling, etc. It was, till lately, customary to regard 

 such faults in milk as due to the nature and condition 

 of the food, the nature of the soil, and, above all, to 

 illness or disease in the cow to everything, in short, 

 except the true cause, viz. dirt. We now know, 

 however, that such faults in milk are due to dirty 

 and careless handling, or, more exactly stated, to 

 micro-organisms which gain access to the milk when 

 it is dirtily treated. Indeed, the best proof of this is 

 to be found in the fact that improved dairy practice 

 has rendered such faults of extremely rare occurrence. 

 In large and modern dairies they are practically 

 unknown, and it is only in small dairies, where 

 unfortunately extremely primitive methods too often 

 obtain, that they still occur. 



Occurrence of Bacteria. Before more particu- 

 larly dealing with these micro-organisms, let us see 

 where they are to be found. To this a simple answer 

 may be given. Modern investigations have shown 

 that their presence is well-nigh universal. In the air, 

 in the soil, and in water they are widely distributed. 

 In the air they are to be counted by thousands in 

 every cubic yard, while in like quantities of water 

 and the soil millions of them exist. It is true 

 that, under certain circumstances, air may be, if not 

 absolutely, yet comparatively, free of them. For 

 example, it would seem highly probable that in air 



