466 BACTERIA PATHOGENIC TO MAN 



wiped with a clean damp cloth and the milkers should thoroughly 

 wash and wipe their hands before commencing milking. The pails 

 and cans should not only be carefully cleansed, but afterward scalded 

 out with boiling water. The washing of the hands would lessen the 

 number of ordinary filth bacteria in the milk, and diminish risk of 

 transmitting to milk human infectious diseases like scarlet fever, diph- 

 theria, and enteric fever, by the direct washing off of the disease germs 

 from infected hands. It would also inculcate general ideas of the neces- 

 sity of cleanliness and of the danger of transmitting disease through 

 milk. The value of cleanliness in limiting the number of bacteria is 

 demonstrated by the figures contained in the tables. 



Summary and Conclusions. Because of its location and its hairy 

 covering the cow's udder is always more or less soiled with dirt and 

 manure unless cleaned. On account of the position of the pail and the 

 access of dust-laden air it is impossible to obtain milk by the usual 

 methods without mingling with it a considerable number of bacteria. 

 With suitable cleanliness, however, the number is far less than when 

 filthy methods are used, there being no reason why fresh milk should 

 contain in each cubic centimetre on the average, more than 12,000 

 bacteria per c.c. in warm weather and 5000 in cold weather. Such milk, 

 if quickly cooled to 46 F., and kept at that temperature, will at the end 

 of thirty-six hours contain on the average less than 50,000 bacteria per 

 cubic centimetre, and if cooled to 40 F. will average less than its 

 original number. 



With only moderate cleanliness such as can be employed by any 

 farmer without adding appreciably to his expense, namely, clean pails, 

 straining cloths, cans or bottles, and hands, a fairly clean place for 

 milking, and a decent condition of the cow's udder and the adjacent 

 belly, milk when first drawn will not average in hot weather over 30,000, 

 and in cold weather not over 25,000 bacteria per cubic centimetre. 

 Such milk, if cooled to and kept at 50 F., will not contain at the end 

 of twenty-four hours over 100,000 bacteria per cubic centimetre. If 

 kept at 40 F. the number of bacteria will not be over 100,000 per 

 cubic centimetre after forty-eight hours. 



If, however, the hands, cattle, and barns are filthy, and the pails are 

 not clean, the milk obtained under these conditions will, when taken 

 from the pail, contain very large numbers of bacteria, even up to a 

 million or more per cubic centimetre. 



Freshly drawn milk contains a slight and variable amount of bac- 

 tericidal substances which are capable of inhibiting bacterial growth. 

 At temperatures under 50 F. these substances act efficiently (unless the 

 milk is filthy) for from twelve to twenty-four hours, but at higher tem- 

 peratures their effect is very soon completely exhausted, and the bac- 

 teria in such milk will then rapidly increase. Thus the bacteria in fresh 

 milk which originally numbered 5000 per cubic centimetre decreased 

 to 2400 in the portion kept at 42 F. for twenty-four hours, but rose 

 to 7000 in that kept at 50 F., to 280,000 in that kept at 65 F., and 

 to 12,500,000,000 in the portion kept at 95 F. 



