*No. XIII.--Urine* in forty-four hours showed a very slight amount of sediment. During the next two days the sediment very slightly increased, but was still small in amount. At the expiration of fifteen days, no further increase in the turbidity having taken place, the fluid was examined. The vacuum was still partially preserved, as evidenced by the rapid inbending of a portion of the neck of the flask after it had been carefully made red-hot. When opened, the odour of the fluid was stale, but not fœtid, and its reaction was still faintly acid. On microscopical examination _Bacteria_ and _Torulæ_ were found in tolerable abundance. *No. XIV.--Hay Infusion* in forty-four hours showed a very slight amount of turbidity. In sixty-eight hours the turbidity was most marked, and there was also a small amount of sediment. In another twenty-four hours it was noticed that the colour of the fluid had become much lighter, whilst the turbidity and sediment had increased. It subsequently continued in much the same state, and the flask was opened on the sixteenth day. The vacuum was found to be almost wholly impaired, whilst the odour of the fluid was sour, and not at all hay-like. On microscopical examination _Bacteria_, _Vibriones_, _Leptothrix_, and _Torulæ_, were found in abundance, and the former were very active. *No. XV.--Turnip Infusion* after forty-eight hours showed a well-marked turbidity. In seventy-two hours the turbidity was more marked, and there was a slight amount of sediment. The turbidity also increased during the next twenty-four hours; though, after that, the infusion seemed to undergo no further change. The flask remained in the warm bath for fifteen days, when the fluid was examined. Its odour was not fœtid, but was somewhat like that of baked turnip. _Bacteria_ and _Vibriones_ existed in abundance, though their movements were extremely languid. SECOND SET OF EXPERIMENTS (XVI.–XXI.). _b. Fluid in contact with Ordinary Air and its Particles; Neck of Flask Sealed after the Fluid had become Cold._ *No. XVI.--Simple Turnip Infusion* in twenty-four hours had undergone no apparent change. In thirty-six hours there was slight turbidity, and in forty-eight hours this was most marked and uniform. When the flask was opened, after seventy-two hours, there was an outrush of very fœtid gas; the reaction of the fluid was acid, and, when examined microscopically, it was found to contain multitudes of very languid _Bacteria_. *No. XVII.--Neutralized Infusion of Turnip + 1/2 gr. of Cheese*,[53] in thirty-six hours showed a well-marked pellicle.[54] When the flask was opened, after seventy-two hours, there was a violent outrush of gas, though the fluid was still neutral. Portions of the thick pellicle were found, on microscopical examination, to be made up of _Bacteria_, _Vibriones_, and an abundance of long, interlaced _Leptothrix_ filaments. _Bacteria_ also existed abundantly in the fluid, though their movements were very languid.