The best known artificial bate is "Oropon," which consists of a mixture of pancreatin or trypsin, ammonium salts, and a large quantity of sawdust, the last-named merely acting as a mechanical agent. The enzyme, pancreatin, is the active ingredient, and may be prepared from the intestines of the pig. It has the effect of breaking up the albuminous matters of hides and skins, which are rapidly reduced to a soft and supple condition, while the ammonium salts cleanse them. The quantities used vary according to the degree of suppleness required in the finished leather. The patentee and vendor of this proprietary article claims that it is suitable for all classes of leather. Hides for sole leather are sometimes treated with a weak "Oropon" liquor in Continental tanneries and, as a result of the cleansing properties of this bating material and its effect in opening up the fibres, the tannage proceeds rapidly. The use of enzymes for bating was discovered by an English leather manufacturer and chemist, who did not take out a patent for his invention, probably because he had previously patented and worked on a commercial scale a bacterial bate which gives very good results but requires much skill in application. The artificial product, "Oropon," has many advantages over excrements. It is simpler, cleaner, and more rapid in working, and never damages the grain of the skin. On the contrary, great care and experience are needed in using excrements, and the skins may be so badly damaged through negligence as to be almost worthless. Bate burns are fairly frequent when dung is used, and are generally due to hard pieces being insufficiently broken up and diffused in the liquor. Other useful artificial products are: "Erodin," and "Puerine," a patented American product which consists of a weak organic acid and a small proportion of molasses. Possibly, malt enzymes or diastase could be utilised for the manufacture of an artificial bate or puer, although they would not be so effective as animal products. Where hides and skins have been treated with Oropon, they may be transferred to the tan liquors after being rinsed in water, although it is better to submit them to the operation of scudding.