Such are Mycoderma aceti, which converts the alcohol of fermented beverages into vinegar; Micrococcus ureae, which converts the urea of urine into carbonate of ammonia, and Micrococcus nitrificans, which converts nitrogenized matters into intrates, etc.

These pellicles are made up of myriads of globules of Mycoderma aceti.

The vats were often infested by small worms ("vinegar eals") which disputed with the mycoderma for the oxygen, killed it through submersion, and caused the loss of batches that had been under troublesome preparation for months.

Since Mr. Pasteur's researches, the Mycoderma aceti has been sown directly in the slightly acidified wine, and an excellent quality of vinegar has thus been obtained, with no fear of an occurrence of the disasters that accompanied the old process.

Finally, we may sow the nitric ferment in calcined earth and cause nitrification to occur therein as surely as we can bring about a fermentation in wine by sowing Mycoderma aceti in it.