In a well-regulated meat-packing establishment the loss from ham souring is usually figured at about one-tenth of 1 per cent of the total weight of hams cured. At first thought this would seem but a small loss, but when one reflects that in a single large packing establishment some 3,000,000 hams are cured during the year, the loss, when figured out, is considerable. Taking 15 pounds as the average weight of a ham, 3,000,000 hams would represent 45,000,000 pounds of meat. Figuring the loss from souring on the basis mentioned, the amount of meat condemned and destroyed during the year would be 45,000 pounds. Assuming that hams sell at an average wholesale price of 15 cents a pound, the yearly loss for a single plant which cures 3,000,000 hams a year would be nearly $7,000. While one-tenth of 1 per cent of the total weight of hams cured would represent the loss from souring in a well-regulated establishment, statistics obtained through Government meat inspectors show that 0.25 per cent would more nearly represent the loss for the entire country. During the fiscal year from July 1, 1908, to June 30, 1909, some 670,000,000 pounds of hams were placed in cure in packing establishments subject to Government inspection. Estimating the loss from souring at 0.25 per cent, the total amount of meat condemned and destroyed as sour would be 1,675,000 pounds. At 15 cents a pound the total annual loss from ham souring in packing houses subject to Government inspection would figure up something over a quarter of a million of dollars. The problem of ham souring, therefore, is quite an important one from a practical and financial standpoint; but aside from these considerations it is also a subject of considerable scientific interest, and in view of the fact that all sour meats are condemned under the Federal regulations governing meat inspection it has seemed fitting that this question should be made the subject of scientific investigation on the part of the Bureau which is charged with the administration of this inspection. The investigation reported in this paper has been conducted chiefly along bacteriological lines, and has been confined entirely to the wet method of curing hams, as this method is the one generally used in American packing houses. METHOD OF CURING HAMS. In order to make clear certain points in regard to the nature and occurrence of ham souring and to insure a better understanding of the experiments which are to be described later, it would seem best to begin with a brief outline of the method of curing hams as practiced in the larger packing establishments of the country. This description is merely a general outline of the method of preparing hams for cure and the method of handling hams while in cure, and deals chiefly with those points that bear on the question of souring.