On this principle, in preparing an artificial puer for hides, and in accordance with the nature and preliminary treatment of the raw material, and the requirements put forward in respect of the finished product, the bacterial puer, nutrient medium or culture is mixed with the corresponding digestive juices, or with purified animal or vegetable enzymes, as well as with fat decomposing media, if necessary, such as ground castor-oil seeds, hemp seed or the like, or with extracts of same, or with gall. Where it seems necessary, substances capable of dissolving lime may also be added, for example, sugar, molasses, salts of ammonia, organic acids, or the corresponding salts or the like. Finally, also, the several operations may be carried out independently of one another, it being in such case again advisable to adhere to the processes going on in the intestines. If, for instance, specially hard goat skins are to be pulled down strongly by puering, it is advisable to add to the nutrient medium of the bacteria a little papayotin or papain, either--according as rendered necessary by the local conditions--in the preparation of the bacterial puering liquor, or during the propagation of the bacteria. If the fells are less hard so that less pulling down is required, the hides are first treated with a weak solution of the digestive ferments, and then with the bacterial liquor. In this way excessive digestive action is counteracted in good time. Sheep and goat skins that are particularly rich in fat are immersed in a bacterial puering liquor, containing ground castor-oil seed or castor-oil cake in suspension. The fat-decomposing ferment contained in this meal then comes into immediate action, and the liberated fatty acids form readily soluble soaps with the ammonia, originating from the degradation of the proteid substances, and with the allied bases. Extensive practical experiments have also shown that, in the case of very fat skins, the action of the bacterial puer is increased by mixing a suitable salt of sulpho-ricinoleic acid with the puering liquor, or by washing the skins with solutions of similar soaps either before they are immersed in the puering liquor, or subsequently. Local conditions, and the requirements laid on the finished leather, must decide which of these methods is specially advisable. In any event, however, the combinations of the bacterial puer afford a means of obtaining an increased puering effect in many cases where puering with the separate auxiliaries mentioned does not produce a sufficient result. _Claim._--In the method of puering hides wherein bacterial cultures, their metabolic products and enzymes are employed, the combined use with these agents of digestive juices, mixtures of digestive enzymes or pure digestive enzymes (and, if desired, of fat-decomposing substances), either simultaneously with said agents or subsequently thereto. CHAPTER IX. DRENCHING.