14 THE NATURE-STUDY REVIEW [6:1-Jan., 1910 



thrusting' the hand clown into the silage. That carbon dioxide 

 is produced in the pail may be shown by putting a spoonful 

 of lime water into an open bottle and placing it inside the cov- 

 ered pail. After a time take it out and shake it. The lime 

 water will become milky white, showing the presence of the 

 gas. This carbon dioxide in the silo kills the germs of fer- 

 mentation which were present when the corn was packed in it, 

 just as it would kill a man who might go into the silo during 

 the first few days without ventilating it. That is, the germs of 

 fermentation are stifled by lack of oxygen. In the same way 

 the plant cells are killed. Hence carbon dioxide gas accom- 

 plishes for the silo what cooking does in the case of canning 

 fruit and vegetables in the household. It is most essential that 

 the silage should be packed germ-tight, or as we usually say 

 air tight, because air passing in would carry not only oxygen 

 but also germs of molding, fermentation and decay with it. 



When all life in the silo ceases, heat is no longer produced 

 and the temperature very gradually tends to become that of the 

 surrounding air. The chemical changes which were produced 

 during the first few days by the living cells and by the ferments, 

 appear to make the mass more palatable, more digestible, and 

 in every way a better food. If the process were allowed to go 

 on farther, it would spoil the food; but in a large, well-packed 

 silo, the process may be arrested completely at the right stage 

 and the silage may be kept without change indefinitely. 



The experiment in the pail should be carried on for many 

 weeks to show what sour and mouldy stuff would be pro- 

 duced in a silo if it were not big enough and not packed tight 

 enough to completely arrest the chemical action. Of course 

 ferments attack the top layer of silage in all cases and make it 

 sour and musty. This action however takes place only in the 

 upper layer. When feeding from the silo begins we reject 

 the top layer and afterward the cattle use it fast enough so that 

 no silage remains on the surface long enough to spoil. 



In Europe, silos were dug in the earth fully 2000 years 

 ago for preserving certain foods, but the first silo in America 

 was built in 1879. They have been perfected and have come 

 into general use only during the last 15 or 20 years. 



Good silage is good food for milk cows, and no reason- 

 able objection has thus far been made to it. 



The silo suggests several kindred studies. After mowing 



