[52] Flask still in my possession, unopened.
[53] The filtered infusion of turnip was neutralized by liquor potassæ. The cheese (Cheddar) was new and not in the least mouldy.
[54] The fluid itself being somewhat opaque, the first stages of increased turbidity from presence of Bacteria could not be detected.
[55] This again is a most instructive experiment when compared with Nos. XVI. and XX., in which portions of the same infusion were employed. The results in No. IX. would lead us to believe that a vegetable infusion which does not ferment, does, nevertheless, undergo some changes in molecular composition, and this notion seems to derive confirmation from the present experiment. Some of the same solution which has been kept for a time (twelve days) from contact with atmospheric particles, subsequently, even when fully exposed to the air, undergoes no apparent change for six days, and then, instead of becoming filled with Bacteria, swarms only with Torulæ. Yet the infusion in this condition was perfectly capable of nourishing Bacteria, as I subsequently proved by inoculating it. Why then was it not inoculated by the living Bacteria, with which the air is thought by some to be teeming?
[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.
[57] The condition of the fluid, and the nature of its contents, were very similar to that met with in No. XXI.
[58] Still in my possession, unopened. In all probability the flocculi which formed would be found to be similar in their microscopical, as they certainly were in their naked-eye characters, to those met with in No. XXXV.
[59] Experiment No. 8, recorded in ‘Nature,’ 1870, No. 36, p. 194, may be compared with this and No. XXXIII.
[60] This experiment should be compared with Nos. XVIII. and XXXIII. It seems to show that if some fermentable fluids can be kept for a time under conditions in which they will not ferment, the constitution of the fluid, instead of remaining the same, undergoes a slow alteration by which it is rendered absolutely less fermentable, even when exposed to the most favouring influences.
[61] After this experiment had been completed, a fresh-filtered infusion of turnip was placed in the same flask (having the neck open just beyond its second bending), and after having been boiled for a few minutes it was immersed in the same water-bath. This fluid became turbid in thirty-six hours, and was then found to contain multitudes of Bacteria; and the characteristic odour of the turnip infusion was still appreciable.