94 A CHEMICAL SIGN OF LIFE 



air free from carbon dioxide, and a drop of barium 

 hydroxide is introduced at the top of the tube in each 

 chamber. If the crushed seed gives off more carbon 

 dioxide than the uncrushed, as evidenced by a larger 

 deposit of the carbonate on the top of the drop in the 

 chamber containing the crushed seed, the seed is alive. 

 If the seeds are alive, such a distinction in the carbon 

 dioxide output will be noticeable in a few minutes in 

 some cases, or in an hour or more in other cases, all 

 depending on the size, the number, and the kind of seed 

 we are testing. With several seeds, as with the fresh 

 nerve of a frog, we can detect vitality in this way in a 

 few minutes. 



