The small opening is very efficient in keeping the dirt out of milk.] =Sanitary milk pails.= The entrance of organisms into the milk can be greatly reduced by lessening the area of the milk pail exposed to the dust shower. To accomplish this purpose a number of so-called sanitary or hygienic milk pails have been devised. In some cases, these are the regular type of pail provided with a cover having a small opening through which the milk is received. In other cases, a strainer is interposed so as to remove more effectually the coarse particles. While pails of this type are successful in the removal of a large part of the dirt, and consequently reduce materially the bacterial content of the milk, yet they must be of simple construction, so that they can be kept in a clean condition in order to adapt them for general practical use. The use of such a utensil increases materially the keeping quality of the milk. [Illustration: Fig. 13.--Sanitary Milk Pails. The Stadtmueller pail and the Truman pail, two of the most practical of the small-topped pails.] Stocking has shown that under ordinary barn conditions, the use of small-topped pails reduced the number of bacteria 95 per cent; with dirty cows the reduction in bacteria amounted to 97 per cent. A six-inch opening presents only one-fourth as large an exposure as a twelve inch, so that the reduction in bacterial content is greater than the lessening in the size of the openings of the pails. The ordinary pail receives dust not only from the udder, but also from the flank which is usually a more important source of contamination than the udder itself, while the small-topped pail receives only that from the udder. [Illustration: Fig. 14.--use of Sanitary Milk Pails. The open pail is fully exposed to the falling dust while the hooded pail excludes much of the dust and dirt coming from the animal.] =Milking machines.= Where the milk is removed from the udder by machine methods, instead of by hand, it is possible to eliminate nearly all external contamination from the animal and her surroundings. The only opportunity for infection is then through the leakage of air around the teat cups. Care should be taken to see that the teats are in a clean condition before applying the suction cups. The main problem in the use of a milking machine is to keep the apparatus in an aseptic condition. Immersion of the teat cups and the rubber connections in lime water, brine solution, or other mild antiseptics, prevents bacterial development. Hastings has found that milk having a germ content of less than 10,000 bacteria per cubic centimeter may be produced by the use of a properly handled milking machine.