The hides or skins are then dipped into the concentrated decoction for a short time, according to the state of development of the bacteria; or the decoction can be diluted and the hides be then immersed therein for a greater length of time. The further treatment is then carried out in exactly the same way as though the hides or skins had been treated in dog-dung lye, with the exception that the duration is shorter. In case the pure culture of the bacteria is to be dispensed with, and it is only desired to obtain an advantage over the existing methods in so far as to obtain, on the one hand an artificial increase of the ooze medium viz. the number of useful bacteria and their products existing in the dog dung, by providing a suitable culture bed, and on the other hand to be in a position to limit oneself to the best initial material, the process can be carried out by starting with a practically proved dog dung, therefore in particular the white kinds, and the bacteria are caused to propagate in a decoction such as above described. Afterwards it is advantageous to effect the killing of the detrimental bacteria by a small addition of acid, such as 0·5 per cent. of dilute sulphuric acid or equivalent materials, as in this case the useful bacteria are also the most enduring. The more useful bacteria show, in particular in the presence of alkalis, the same behaviour. For example, the more useful bacteria arrive at development equally with the detrimental ones, if to the described culture bed be added 0·5 per cent. of carbonate of soda, while the useful bacteria preponderate to a considerable extent, and the detrimental ones are practically unimportant, if the additions of carbonate of soda be raised to about one per cent. The pure cultures of the bacteria may be preserved in a suitable liquid or solid material, and brought on the market in a suitable packing. In order to obtain a product which shall both be durable, and capable of being delivered in definite doses, sterilized bran, flour, etc., can be inoculated with definite quantities of the pure cultures, and the percentage of water be reduced, by drying, pressing, etc., to under a certain percentage (10 to 12 per cent.) which will not allow of, or will retard the evolution of germs. The bacteria may also, after having been properly developed, especially after having created a sufficient quantity of their products, be killed, for instance by heating, and the resulting stuff be brought on the market in liquid or solid form, as an effectual lye or brine, it having been found that the liquids containing the said bacteria do not lose their effect if they are sterilized and the bacteria thereby killed, provided that a sufficient number of bacteria has been produced.