104 BACTERIQLQGY. 



In the fermentation of cellulose, a,naero.bic bacteria play 

 a most important r61e. The cellulose is first conyerted into 

 sugar, which in turn yields butyric acid, marsh-gas, and 

 diverse other products. The changes that take place in the 

 production of sauer-kraut, ensilage, etc., are similar to that 

 just fmentioned. The cellulose is softened, and partially 

 fermented with the production of butyric and lactic acids. 

 In the ripening of cheese, similar decomposition products 

 are formed out of the casein. The retting of hemp and flax 

 is a change analogous to the fermentation of cellulose. The 

 fibres are held together by a cementing substance, calcium 

 pectate, which is removed by allowing the material to soak 

 in water. The intercellular material is not dissolved by the 

 water, but is digested, or dissolved by the action of butyric 

 acid bacteria. 



Viscous or slimy fermentation.— It not infrequently hap- 

 pens that milk, urine, beer, wine and dilute sugar solutions 

 take on a slimy or i"opy consistence. This is due to the 

 presence and development of certain bacteria. As might 

 be expected a very large number of wholly different organ- 

 isms are capable of imparting a slimy character to these 

 several liquids. It may happen that such bacteria will de- 

 velop in sausage, bread, or in biscuits. In such cases, on 

 breaking some of the material and slowly drawing the 

 pieces apart, they will be seen to be connected by numerous, 

 fine, cobweb-like threads. The slimy covering of the ton- 

 gue, teeth, etc., in many fevers, is probably due to organ- 

 isms of this kind. 



The slimy character may be due to one of two causes. 

 In the first place, the organism may secrete, of throw oif a 

 slimy product. This material passes out into the surround- 

 ing liquid and is no longer connected with the cell. This 

 condition is analogous to the secretion of mucin by the cells 

 of the mucous membrane. On the other hand, the sliminess 

 may be due to the formation of capsules. It has been 



