──────────────┬───────┬───────┬───────┬────────┬───────┬─────────── Age of culture│Culture│Culture│Culture│Average.│Medium.│Acidity of (days). │ A. │ B. │ C. │ │ │ culture. ──────────────┼───────┼───────┼───────┼────────┼───────┼─────────── │ │ │ │ │ │_Per cent._ 2 │ 0.038 │ 0.030 │ 0.040 │ 0.036 │ 0.009 │ 0.027 4 │ .105 │ .100 │ .102 │ .102 │ .009 │ .093 6 │ .106 │ .110 │ .109 │ .108 │ .009 │ .099 8 │ .124 │ .115 │ .117 │ .119 │ .009 │ .110 10 │ .128 │ .130 │ .126 │ .128 │ .009 │ .119 12 │ .129 │ .120 │ .129 │ .126 │ .009 │ .117 19 │ .126 │ .125 │ .125 │ .125 │ .009 │ .116 33 │ .125 │ .123 │ .125 │ .124 │ .009 │ .115 47 │ .122 │ .120 │ .121 │ .121 │ .009 │ .112 61 │ .121 │ .116 │ .119 │ .118 │ .009 │ .109 ──────────────┴───────┴───────┴───────┴────────┴───────┴─────────── From the above table it will be seen that the maximum acidity was reached at ten days, after which there was a gradual reduction in the acidity, due probably to the formation of ammonia compounds. PATHOGENIC PROPERTIES. Rabbits, guinea pigs, and white mice were inoculated and fed with cultures of the bacillus without effect, from which it would appear that the bacillus possesses no pathogenic or disease-producing properties. NATURE OF THE BACILLUS. The bacillus is essentially a saprogenic bacterium with zymogenic properties. A preliminary study of the chemical changes which take place in sour hams shows that these changes are of a putrefactive nature. Hams which had undergone spontaneous souring were compared with hams which had been artificially soured by inoculation, and the chemical changes were found to be identical. A chemical study was also made of the changes taking place in egg-pork cultures of the bacillus at different stages of growth, and these changes were found to be of a putrefactive nature and similar in character to the changes which occur in sour hams. Among the putrefactive products formed by the growth of the bacillus in the egg-pork medium were indol, skatol, volatile fatty acids, skatol-carbonic acid, and hydrogen sulphid.[4] [4] The tests for the putrefactive products formed by the growth of the bacillus in the egg-pork medium were made by P. Castleman, of the Biochemic Division, who also determined the percentage composition of the gas formed by the growth of the bacillus in the glucose-pork-bouillon medium. [Illustration: BUL. 132, BUREAU OF ANIMAL INDUSTRY, U. S. DEPT. OF AGRICULTURE. PLATE IV.