88 A CHEMICAL SIGN OF LIFE 
an appearance. The seeds really respire. Waller con- 
sidered that our present chemical technique is not refined 
enough to reveal to us the smallest and most infinitesimal 
chemical changes which may be going on in the appar- 
ently dry and perfectly dormant seed. He based his 
hypothesis on two considerations: First, was the fact 
that the seeds wear out, as shown by their losing their 
power of germination and growth in proportion to the 
length of time they have been kept. The deterioration 
is more or less rapid, according to the nature of the 
seed and the character of the protective.coats, but in 
every instance there is deterioration sooner or later. 
He attributes this gradual deterioration to chemical 
activity in the seed. 
In the second place, there was the fact, which he 
showed by his electrical method, that a living seed not 
only differs from the dead one in respect to its electrical 
response, but that the amount of its response varies 
according to its age. Thus, if he took a living seed, a 
dead seed killed by heat, and a very old Egyptian seed 
from about the Twelfth Dynasty (about 4,400 years 
old) and determined their electrical response, he found 
a very interesting result. The first, or living, seed gave 
a large electromotive force, while the others, the old 
as well as the dead, gave none. If he took a group of 
seeds from crops of different years, he found that there 
was also a gradual decline in the electrical response as 
the seed became old. He considered this electrical sign 
as the expression of the chemical changes which cannot 
otherwise be determined, and such a sign of death, 
according to him, is manifested long before microscopic 
or chemical changes can be detected. 
