ioo A CHEMICAL SIGN OF LIFE 



at every point Waller's electrical test, is shown to be 

 whether or not the tissue respiration can be accelerated 

 by an injury. And we can measure this with our new 

 apparatus, the biometer, which thus justifies its name, 

 although its applicability is far greater than merely 

 testing the degree of vitality of a tissue. 



We have now to compare for a moment this criterion 

 of life the chemical with other criteria which have 

 been proposed, and to see whether it lacks anything of the 

 precision of these other methods, and whether life can be 

 shown to exist by other methods where we cannot prove 

 its existence by ours. There is one criterion other than 

 the obvious one of growth which has been proposed to 

 determine whether a seed or other living thing, or piece 

 of a living thing, is alive or not. That is the criterion 

 suggested by Waller. It is the electrical sign of life. 

 Waller discovered a very remarkable electrical sign of 

 life, which may be described as follows : Two electrodes 

 are placed on opposite sides of a garden pea which is 

 living, the electrodes being connected on the one hand 

 with an induction coil and on the other with a sensitive 

 galvanometer. A single induction shock is then sent 

 through the pea. If the pea is alive, this shock is fol- 

 lowed by a remarkable outburst of electromotive force 

 in the pea. A current suddenly blazes out, as is shown 

 by the deflection of the galvanometer. It is as if the 

 pea jumped when stimulated. This current sometimes 

 travels in the same direction as the induction shock, 

 and sometimes in the opposite direction. It is of momen- 

 tary duration. Waller calls it the blaze current. As 

 long as the seed lives, you get it; when the seed dies, you 

 do not get it. The dead or anesthetized seed does not 



