*No. XX.--Simple Turnip Infusion* in twenty-four hours showed a very slight amount of turbidity; in thirty-six hours this had increased, and in forty-eight hours there were multitudes of curdy flocculi floating in a tolerably clear fluid. The flask was opened after seventy-two hours, when there seemed to be only a very slight inrush of air. The odour of the fluid was somewhat fœtid, and its re-action was acid. There were multitudes of _Bacteria_ and _Vibriones_, partly separate and partly aggregated (constituting the flocculi above mentioned). The separate _Bacteria_ exhibited only very languid movements. *No. XXI.--Neutral Turnip Infusion + 1/2 gr. of Cheese*, showed a well-marked pellicle on its surface in twenty-four hours. In thirty-six hours the first pellicle had, in great part, sunk to the bottom of the flask, though its place on the surface was already taken by a new, though thin, scum-like layer. After seventy-two hours, the flask was opened; there was _no fœtid_ odour of the fluid, and its re-action was _still neutral_. Examined microscopically the fluid showed an abundance of Bacteria, and also of short monilated filaments. There were, however, none of the ordinary kind of _Vibriones_, and no _Leptothrix_. All the _Bacteria_ exhibited very languid movements. THIRD SET OF EXPERIMENTS (XXII.–XXX.). _a. Fluid exposed to Air in a Flask with a short Open Neck._ *No. XXII.--Urine* in twenty-four hours showed no change; though in forty-six hours the turbidity was well marked.[56] Examined microscopically it was found to contain an abundance of _Bacteria_. [56] Some of the same fluid, exposed in a similar flask, without previous boiling, became turbid in eight hours, and lighter in colour; whilst, after twenty hours, the turbidity was extremely well-marked. _b. Fluid in contact with Ordinary Air and its Particles; Neck of Flask Sealed after the Fluid had become Cold._ *No. XXIII.--Urine* in eighteen hours showed a distinct pellicle, though there was not much general turbidity. During the next few days the old pellicle fell to the bottom, and a new one formed. _c. Fluid in a Bent Neck Flask, having Eight acute Flexures._ *No. XXIV.--Urine* in forty-eight hours showed no change. After twelve days there was still no general turbidity, though there was a slight flocculent deposit of an uncertain nature. Two days afterwards the flask was broken, when the odour of the fluid was still found to resemble that of fresh urine, and its re-action was acid. The flocculi were made up of granular aggregations, in the midst of which were a few bodies closely resembling _Torulæ_, though they were somewhat doubtful in nature. Neither _Bacteria_ nor _Vibriones_ could be found. The flask, having a short open neck, was then replaced in the warm bath. In sixteen hours the whole fluid had become turbid; it was also slightly fœtid; and on microscopical examination it was found to be swarming with _Bacteria_, _Vibriones_, and _Leptothrix_.