46 THE STORY OF GERM LIFE. 



the warm sun and very rapidly decay. Bacteria 

 make their way into the sponge and thoroughly 

 decompose the soft tissues. After a short putre- 

 faction of this sort the softened organic matter 

 can be easily washed out of the skeleton and 

 leave the clean fibre ready for market. 



Leather preparation. The tanning of leather 

 is a purely chemical process, and in some pro- 

 cesses the whole operation of preparing the 

 leather is a chemical one. In others, however ; 

 especially in America, bacteria are brought into 

 action at one stage. The dried hide which comes 

 to the tannery must first have the hair removed 

 together with the outer skin. The hide for this 

 purpose must be moistened and softened. In 

 some tanneries this is done by steeping it in 

 chemicals. In others, however, it is put into 

 water and slightly heated until fermentation 

 arises. The fermentation softens it so that the 

 outer skin can be easily removed with a knife, 

 and the removal of hair is accomplished at the 

 same time. Bacterial putrefaction in the tannery 

 is thus an assistance in preparing the skin for 

 the tanning proper. Even in the subsequent 

 tanning a bacterial fermentation appears to 

 play a part, but little is yet known in regard 

 to it. 



Maceration of skeletons. The making of skele- 

 tons for museums and anatomical instruction in 

 general is no very great industry, and yet it is 

 one of importance. In the making of skeletons 

 the process of maceration is commonly used as 

 an aid. The maceration consists simply in allow- 

 ing the skeleton to soak in water for a day or 

 two after cleaning away the bulk of the muscles. 

 The putrefaction that arises softens the connect- 



