27 



Freshly drawn milk that has been produced' 

 Number of Bacte- under strictly sanitary or aseptic methods should 

 ria in Milk. contain but a few hundred bacteria to the cubic 



centimeter. Such milk will keep for a consid- 

 erable length of time, especially if held at a low temperature. 



Country milk produced by ordinary methods, but drawn from 

 reasonably clean cows, kept in passably clean stables, ought not as a 

 rule to contain more than 5,000 to 25,000 bacteria per cubic centi- 

 meter when first placed upon the market. Such milk, if free from 

 objectionable flavor and odor, may be regarded as satisfactory for 

 general consumption. 



Country milk, produced under conditions ordinarily prevailing, is 

 likely to contain 50,000 or more bacteria per cubic centimeter when 

 first offered for sale. Milk offered in large cities often contains 

 from several hundred thousand to many million bacteria to the cubic 

 centimeter. The city of Boston forbids the sale of milk containing 

 over 500,000 bacteria to the cubic centimeter. 



I. A large number of bacteria in market 



Meaning of Bacte- milk (100,000 or more to the cubic centime- 



ria in Milk. ter) means that the milk is old, or that it has 



been kept at too high a temperature, or that it 



has been produced under unsanitary conditions.' 



2. Strictly fresh milk contains, as a rule, comparatively few lactic 

 acid organisms (rarely above 25 or 30 per cent, of the total number 

 present). The few lactic acid bacteria develop rapidly, especially at 

 ordinary temperatures, and at the end of two days very largely 

 overcome the other species. Milk containing chiefly lactic acid 

 organisms is usually old, but not necessarily dirty. 



3. The presence of many liquefiers is an indication that filth has 

 gained access to the milk. A noticeable percentage of lic^efiers in 

 milk containing a high total count is very indicative of filthy 

 conditions.' 



'High temperature is a more potent cause of the rapid increase of bacteria than unsani- 

 tary conditions, unless the latter are particularly bad. 



-These interpretations are based particularly upon the researches of Conn. See Fifteenth 

 report of the Storrs experiment station, pp. .33-98. 



