SS8 MICROBIOLOGY OF SPECIAL INDUSTRIES. 



but it is probable that the effects are due to the united action of several, 

 both aerobic and anaerobic. 



Among the forms to which the retting has been attributed are B. 

 amylobacter of van Tieghem, an anaerobic form which attacks the pectic 

 matters and to some extent the cellulose. Granulobacter pectinovorum 

 of Beyerinck and van Delden, also anaerobic, transforms the pectic 

 matters into sugars which it decomposes, producing butyric acid.' 

 Many other forms have been described and part of the work has been 

 ascribed to Mucor, PenicilUum and various molds. 



Cultures of Granulobacter pectinovorum and other forms have been 

 successfully used to hasten the process. 



Tanning. — In the manufacture of leather the hides are received 

 salted or dried, or more usually, fresh from the slaughter house — 

 "green hides." The green hides are thrown immediately into a pit 

 containing a lime solution; the salted and dried are first soaked in water 

 before being placed in the lime pits. The combined action of the hme 

 and bacteria loosens the hair. The liquids in old pits contain large 

 numbers of bacteria and are much more effective than new lime 

 solutions. 



On removaHrom the lime pits the hair is slipped from the hides by 

 hand scrappers. Wool is removed from sheep skins after allowing them 

 to undergo incipient putrefaction in an air-tight room. 



Light hides and skins after removal of the hair are placed in a soak- 

 ing pit for a few hours to remove some of the excess of lime. They are 

 then placed in the bating wheel which is a wooden tank furnished 

 with a large, revolving wooden wheel which keeps the hides in motion. 

 The Uquor in the bating wheel contains pigeon, chicken or dog excre- 

 ments and is kept at about 40°. Rapid bacterial action takes place and 

 the hides "fall" or become soft and most of the lime goes into solution. 

 If left too long in the bating liquor the hides lose weight by destruction 

 of their proteins and may finally be completely dissolved. For this 

 reason the bating process must be closely watched and stopped as soon 

 as the hides are well softened. 



Heavy hides for sole and harness leather do not go through the 

 bating wheel, but are simply soaked and agitated in water to remove 

 the lime. Bating would result in too much softening and loss of hide 

 substance. In some cases a dilute solution of lactic acid is used to 

 de-lime the hides. 



