THE PREPARATION OF PELT 21 



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 subtances, 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 anaerobes, but some may be anaerobic 

 by adaptation. It is probable that aerobic ferments com- 

 mence 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. 



The lime, however, not only limits and selects the 

 course of the putrefaction, but also affords more positive 

 assistance. L,ime plays its own hydrolytic part and assists 

 the depilation by purely chemical action. Lime will unhair 

 without the assistance of bacteria, but its action is slow and 

 forms a minor part of the operation in the average limeyard. 

 This action is due chiefly to its progressive formation of 

 calcium sulphydrate from the cystine group of the softer 

 keratins. L,ime also plays an essential part in assisting 

 the putrefactive fermentation. It softens the keratins 

 and thus assists the bacterial attack, it hydrolyzes other 

 proteids and provides the bacteria with food in solution, 

 the calcium ion increases the proteolytic action of certain 

 enzymes, and finally the apparently inert excess of un- 

 dissolved lime has an accelerating effect on the bacterial 

 activity. 



In the average limeyard these various functions are 

 inextricably mixed up, and it is impossible to assign any 

 definite proportion of the total depilatory effect to any of 

 the factors at work. Lime alone will unhair, bacteria alone 



