A CHEMICAL SIGN OF LIFE. 285 



this method as a means to denote protoplasmic irritability, as 

 long as we can abolish this sign of life by rendering the tissue 

 unexcitable. The nerve, dry seeds, including wheat, oats, rice 

 and several other living tissues from animal and plant kingdoms, 

 if treated with ether, or killed, can never be made to produce 

 more CO 2 by crushing, whereas, a tissue however little CO 2 it 

 may produce normally will give off more CO 2 when crushed, 

 provided it is living. From these general findings, I conclude 

 that this method can be used to detect vitality of protoplasm 

 under normal conditions. 



The details of this simple means of finding the sign of life are 

 as follows: 



The biometer is used. This is an apparatus which has two 

 respiratory chambers, each furnished with a cup in which a drop 

 of barium hydrate can be introduced. With it, the comparative 

 outputs of CO 2 as small as o.ooooooi g. from the two tissues 

 can be estimated simultaneously. 1 Two dry living kernels of 

 the same seed, with equal weights, are chosen. One is placed in 

 the right chamber, and the other is crushed and placed in the 

 left. After the necessary cleaning of the apparatus with CO 2 - 

 free air, a drop of the barium hydrate is introduced upon each cup 

 in both chambers. By watching the drop, it would become 

 obvious that the crushed seed is giving off more CO 2 than the 

 uninjured, as indicated by the speed of formation and quantity 

 of precipitate of the barium carbonate. Not only such distinc- 

 tion between two can be observed, within a few seconds, in the 

 case of the tissue, which normally gives off a comparatively large 

 quantity of CO 2 , but also dead tissue whether or not it gives off 

 CO-2 without crushing, will never produce more CO 2 when 

 mechanically smashed. In other words the phenomenon of 

 production of more CO 2 by crushing is characteristic only of a 

 living tissue. By killing the seeds, and repeating the experi- 

 ment, such a conclusion can easily be confirmed. 



With these facts, I am proposing a new sign of life, namely, 

 a chemical sign of irritability. It is a measurement of CO 2 due 

 to stimulation. It is not exhalation of CO 2 which is character- 



1 The detail of this apparatus is described in Am. J. of Physiol., XXXII., p. 141, 



