The pasteurization of milk and cream intended for consumption as such has now been practised for a considerable period. Many sets of figures are available showing the bacterial content before and after pasteurization with various methods and much information has been obtained relative to the bacterial content of pasteurized milk at the time of delivery. The data on the influence of pasteurization on the bacterial content over considerable periods of time are not so numerous, however, and it was with the idea of securing information under practical conditions on this point that the work herein reported was carried out.

The milk studied was that pasteurized in the market room of the dairy department of the Iowa State College for delivery on the route. Two grades of milk are put out-—the one pasteurized by the vat method and the other by the final package method —and a study was made of each.