1748 Turbevill Needham
 

. . . FOR MY PURPOSE, THEREFORE, I took a Quantity of Mutton-Gravy hot from the Fire, and shut it up in a phial, clos'd up with a Cork so well masticateds that my Precautions amounted to as much as if I had sealed my Phial hermetically. I thus eflfectually excluded the exterior Air, that it might not be said my moving Bodies drew their Origin from Insects, or Eggs floating in the Atmosphere.... I neglected no Precaution, even as far as to heat violently in hot Ashes tht Body of the Phial, that if any thing existed, even in that little portion of Air which filled up the Neck, it might be destroyed, and lose its productive Faculty. Nothing therefore could answer my Purpose of excluding everv Objection, better than hot roast-Meat Gravy secured in this manner, and exposed some Davs to the SummerHeat: and as I determined not to open it, till I might reasonably conclude, whether, by its own Principles, it was productive of any thing, I allow'd sufficient Time for that Purpose to this pure unmix'd Quintessence, if I may so call it, of an animal body.... My Phial swarm'd with Life, and microscopical Animals of most Dimensions, from some of the largest I had ever seen, to some of the least. The very first Drop I used, upon opening it, yielded me Multitudes perfectly form'd, animated, and spontaneous in all their Motions:
I shall not at this present time trouble you with a Detail of Observations upon three or four Scores of different Infusions of animal and vegetable Substances, posterior to these upon Mutton-Gravy; all which constantly gave me the same Phaenomena with little Variation, and were uniform in their general Result: These may better appear at length upon some other occasion; let it suffice for the present to take notice, that the Phials, clos'd or not clos'd, the Water previously boil'd or not boil'd, the Infusions permitted to teem, and then plac'd upon hot Ashes to destroy their Productions, or proceeding in their Vegetation without Intermission, appear'd to be so nearly the same, that, after a little time, I neglected every Precaution of this kind, as plainly unnecessary....
. . . It seems plain therefore, that there is a vegetative Force in every microscopical Point of Matter, and every visible Filament of which the whole animal or vegetable Texture consists: And probably this Force extends much farther; . . .
Hence it is probable, that every animal or vegetable substance advances as fast as it can in its Resolution to return by a slow Descent to one common Principle, the Source of all, a kind of universal Semen; whence its Atoms may return again, and ascent to a new Life.
 

Comment by Thomas Brock

This selection of Needham's is typical of the thinking of the proponents of spontaneous generation. The crucial experimental points are whether or not the -to keep any living things out of the vial after the heating of the vial in hot ashes was really sufficient to destroy all living things within, and whether the cork was able to keep any living things out of the vial after heating. Spallanzani deals with both of these problems in the next article, and in so far as it was possible with 18th century techniques, solves them.