SCIENTIFIC AGRICULTURE. 



tation. Tiie fermenting power of yeast is destroyed by boiling, 

 by alcohol, by many salts and acids, and generally by all those 

 agencies which render albimnn and gluten insoluble. 



Besides yeast, there are several vegetable substances, as 

 gluten, albumen, caseine and fibrine, which, when in a state of 

 decomposition, act as ferments on a solution of sugar. The 

 same effect is produced, also, by animal gluten, albumen, flesh 

 and blood, after putrefaction has commenced. When wine 

 and cider are exposed to the air at a certain temperature, a 

 second fermentation, called the acetous, takes place, and they 

 are changed to vinegar: during this change oxygen is absorbed 

 from the air, and carbonic acid is evolved : " but the apparent 

 cause of the formation of vinegar is the abstraction of hydrogen 

 from the alcohol, so as to leave the remaining elements in such 

 proportions as to constitute acetic acid. The presence of nitro- 

 gen seems to be necessary to the composition of all ferments. 

 The precise nature of the changes which take place during 

 fermentation are not yet precisely understood or explained. 



" We can offer no other explanation of these facts of fermen- 

 tation than this, that when a body in a state of progressive 

 change, the particles of which are in a state of motion, is 

 placed in contact with another body, the particles of which 

 are in a state of unstable equilibirum, the amount of motion 

 mechanically communicated to the particles of the latter from 

 those of the former is sufficient to overturn the existing equi- 

 librium, and by the formation of a new compound, establish a 

 new equiblirum more stable under the given circumstances." 



[Turner. 



METAMORPHOSIS OF ORGANIC ELEMENTS. 



There are certain organic compounds which, from the com- 

 plexity of their constitution and consequent weakness of affinity, 

 are peculiarly disposed to decomposition and change of elemen- 

 tary form. Among these are starch, gum, sugar and lignine, 

 the first three of which are composed of the same elements in 

 the same proportions. 



