The extent of our present knowledge of the action of enzymes in puering may be summed up as follows. Active enzymes are produced by bacteria growing in the infusion of dung, in addition to digestive enzymes which may be originally present in the dung; the bacterial enzymes are produced more rapidly in a dilute infusion, as employed in the puer wheel, than in the dung itself. The enzymes are of various kinds, proteolytic, peptolytic, lipolytic, etc., but the proteolytic and lipolytic are the most important. These have a solvent action on the fibres of the skin, but little or no action on the hyaline layer, at the concentration usually found in the puer liquor. The fatty matters and soaps in the skin are acted upon by the lipolytic enzymes, and the fats to some extent emulsified, so that they may be easily removed from the skin by scudding or pressing. It must be clearly understood that enzyme action alone is not sufficient, as has been previously explained, but that the dung enzymes, acting in conjunction with the chemical compounds present, produce the specific puering effect. There is still much work to be done before the action of the enzymes in dung is fully understood, but from the above short account it will be seen that the part they play in the bate is of great importance. CHAPTER VI. ORIGINAL PAPERS ON BATING. The reprints of these papers being no longer available, I have thought it best to print them in the present volume exactly as published, with the exception of the paper entitled “Fermentation in the Leather Industry” from which only so much is reproduced as relates to puering and bating. I. PART OF PAPER ENTITLED “FERMENTATION IN THE LEATHER INDUSTRY.” Read before the Nottingham Section of the Society of Chemical Industry, February 14, 1894. In the next process, that of “bating,” the bacteria play a more important part, and may be put in our second category, viz. helpful to the tanner, though, from the very nature of the material used, it forms a nidus for various putrefactive ferments, and is therefore dangerous. The materials usually employed are bird dung and dog dung; the former of these is sharp and piercing in its action, while the latter has a more softening action on the skin. In both bates, however, a rapid solution of the gelatinous and albuminous hide substance (coriin) takes place. The hide fibres, however, are not attacked until all the nutrient material in the liquid has been consumed by the bacteria.