124 GUIDE TO DAIRYING IN SOUTH AFRICA 



they find themselves, between a plentiful supply of 

 air and its entire absence in a free state. 



Bacteria require food, a suitable temperature to 

 thrive in, and also a certain degree of moisture 

 before they thrive and multiply. Milk contains all 

 these properties in an easily assailable form, there- 

 fore milk becomes an ideal home for these organ- 

 isms to thrive and multiply. Many forms of 

 bacteria which get into milk are harmful to the 

 dairyman. Others again are useful, such as lactic 

 bacteria, which have to do largely with the flavour 

 to be produced in our dairy products. All milk is 

 liable to undergo change through the influence of 

 bacteria. While milk remains in the udder of the 

 cow it is usually free from bacteria, but unless 

 special precautions are taken thousands of bacilli 

 per cubic centimetre will be found in milk soon 

 after it is drawn from the cow. In his book 

 "Elementary Bacteriology" Dr. M. L. Dhingra 

 states, " Milk when secreted from the gland is 

 practically germ-free, but by the time it has entered 

 the pail it is very rich in bacterial contents. These 

 come from all sources : from the milk buckets, the 

 hands of the milker, from the air of the cowshed, 

 and from dirt on the body and udder of the cow." 



These bacteria breed or increase at an enormous 

 rate when the temperature is suited to them, the 

 most suitable temperature being that of blood heat, 

 or a little below. They multiply, breed, or increase, 



