1/8 AGRICULTURAL BACTERIOLOGY. 



ternal opening, and these bacteria, in the warm temperature of 

 the cow's body, multiply rapidly. Bacteria are thus always 

 abundant near the opening of the teat, although inner parts of 

 the duct are comparatively free. In the period which elapses 

 between the milkings they increase rapidly and are sure to 

 contaminate the first jets of milk drawn. This fact has been 

 abundantly proved by analyses. The first lot of milk drawn, 

 called "fore milk," always contains more bacteria than that 

 drawn later in the milking. Toward the close of the milk- 

 ing the bacteria sometimes disappear so that the last milk is 

 actually sterile when it leaves the milk duct. This is not 

 always the case, but the last milk is always purer than the first. 

 For example, in two tests the results were as follows : 



NUMBER OF BACTERIA PER c.c. 



In fore milk, 55,000, at close of milking oo 



In fore milk, 97,000, at close of milking 500 



Wide variations are shown by different tests but these two 

 will illustrate the general phenomenon. Hence it follows that 

 a considerable reduction in the number of bacteria in milk may 

 be effected by simply allowing the first few jets to run to 

 waste. The species of bacteria in the ducts of different cows 

 differs, but it is tolerably persistent in each cow. Indeed each 

 teat may have its own species which remain constant for a long 

 time. 



A greater source of contamination is the dirt which adheres 

 to the body of the cow. To one unfamiliar with the cow in 

 the ordinary barn the amount of filth which it is common to 

 find adhering to the animal, even in good dairies, is surprising. 

 The cows are rarely groomed ; perhaps they are allowed to 

 stand the whole winter without cleaning. Their flanks become 

 covered with a coating of dried excrement, mixed with all sorts 

 of other filth. Every motion the cow makes dislodges some 

 of this filth. Every time she switches her tail during the 



