PLATE I. Fig. 1.—Section of muscular tissue from sound ham, showing muscle fibers cut longitudinally; nuclei sharply defined and cross striation distinct. Fig. 2.—Section of muscular tissue from sour ham, showing muscle fibers cut longitudinally; nuclei undergoing disintegration and cross striation indistinct 16 II. Fig. 1.—Section through muscular tissue of ham which has undergone natural or spontaneous souring, showing distribution of bacilli between the muscle fibers, which are cut obliquely. Fig. 2.—Section through muscular tissue of ham which has undergone natural or spontaneous souring, showing individual bacilli between the muscle fibers, which are cut somewhat obliquely 18 III. Fig. 1.—Section through muscular tissue of artificially soured ham, showing distribution of bacilli between the muscle fibers, which are shown in cross section. Fig. 2.—Section through muscular tissue of artificially soured ham, showing individual bacilli between the muscle fibers, which are cut longitudinally 26 IV. Glucose bouillon culture in Smith fermentation tube at four days 48 TEXT FIGURES. FIG. 1. Cross section through body of ham, with sour areas indicated by shading and dotted lines 11 2. Cross section through body of ham to show method of sampling for chemical analysis 18 3. Cross section through body of artificially soured ham, showing sour areas and points at which cultures were taken 25 4. Diagrammatic views showing construction of ham thermometer 36 5. Ham-souring bacillus (_Bacillus putrefaciens_), grown on egg-pork medium 46 A BACTERIOLOGICAL STUDY OF HAM SOURING. INTRODUCTORY. The souring of hams is a matter of considerable importance to those engaged in the meat-packing industry, and has been the occasion of no little worry, as in even the best-regulated packing establishments the yearly losses it entails are considerable. The subject has given rise to much speculation on the part of those engaged in the curing of meats, as to the cause of the trouble and how it may be remedied, and has received considerable attention in a practical way, but little seems to have been done in a scientific way toward determining the cause and nature of ham souring.