The function of the lime in depilating is complex and has occasioned much discussion. Its main purpose, however, is that of a partial antiseptic. When hides putrefy, one of the first results is that the hair is loosened. In America depilation by "sweating" is carried out commercially by such a mild putrefaction, the lime liquor permits a similar fermentation at a slower rate, and all tannery lime liquors are swarming with putrefactive bacteria. Liming is thus a safer method than sweating, which may be easily carried too far. Various workers have isolated specific organisms--Wood a _bacillus_, Schmitz-Dumont a _streptococcus_--but it seems highly probable that the limeyard bacteria are just the common organisms of putrefaction sorted out or selected by the exact nature of the liquor and the method of working the limes. Many putrefactive bacteria are very adaptable and could easily accommodate themselves in this way. It is known that the exact nature of the culture medium has a great influence on the rate of development of such organisms, and which particular species thrive and obtain predominance in any limeyard will depend upon the amount and nature of the dissolved organic matter available as food, and upon the exact alkalinity and the concentration of other apparently inert substances, such as common salt and sodium, calcium and arsenic salts. Hence no two lime liquors operate alike, and approximate regularity is only assured by systematic method. In handling and shifting, the organisms are subjected to further selection, and the most adaptable survive. It is probable that different species may act symbiotically. The depilating organisms of lime liquors are probably mostly anærobes, but some may be anærobic by adaptation. It is probable that ærobic ferments commence the depilation, but this will be done before the goods are put into work, or at any rate before they reach the limes. More strictly, it is the enzymes secreted by bacteria which are directly responsible for the hydrolytic work; these enzymes are chiefly proteolytic (proteid splitting), but the lipolytic (fat splitting) enzymes have also a place.