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. Lime plays its own hydrolytic part and assists 

 tin- 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 



;ti in sulphydrate from the cystine group of the softer 



keratins. Lime 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, 



calcium ion increases the proteolytic action of certain 



iiK-s, and finally the apparently inert excess of un- 



dissolved lime has an accelerating effect on the bacterial 



:ty. 



In the average- limeyard these various functions arc 



Ably inixi-d iij>, and it is impossible to assign any 



definite proportion of the total depilatory effect to any of 



the factors at work. Lin ( aloiu \\ill unhair, bacteria alone 



