8 



THE SIGNS OF LIFE 



[LECT. 



VoLt 



0150 



do not know beforehand whether it is alive or dead (but which 

 I believe to be dead as it dates from the year 1 860). And at 

 the end of this lecture, if you care to see the 

 trial, I will test some very old seeds indeed, that 

 were given to me by Mr Percy Newberry, who 

 combines the qualifications of botanist with those 

 of Egyptologist. They are seeds collected by 

 himself, and placed by him as dating from the 

 twelfth dynasty, z>., as being something like 4400 

 years old. I need hardly say that no such un- 

 doubtedly old seeds will give any electrical 

 response, nor will they germi- 

 nate. I have previously made 

 both tests. 



0100 



0050 



/99 /9Q /97 /f)6 /95 



[Experiment.] 



the text, is taken as the index of 

 vitality.* 



matters in a future lecture ; 



_, 



I he first seed gives, as you 

 FIG. i. Average electrical response of see, a large electromotive re- 



seeds of five successive years. The T-V ,1 j 



ordinates represent the average vol- s P nse - The other seeds give 

 tage of response, which, as stated in no response at all. The first 



seed is alive, the others are 

 dead. We shall return to these 

 I wish in this first lecture to 

 exhibit to you two other experimental illustrations as typical 

 of the kind of problem and argument with which we have to 

 deal. 



5. Muscle. Muscle is a favourite object of physiological 

 experiment ; it gives sign of life by contracting when it is 

 stimulated either directly, by stimulation of the muscle itself, 

 or indirectly, by stimulation of the nerve that is its motor nerve. 

 And, roughly considered, its mechanical response or contraction 

 is measure of the degree of vitality that it possesses. No one 

 doubts that the contraction of a muscle is sign and proof of its 

 state of life, and that the degree of contraction and the work of 

 which that contraction is capable, are catcris paribus measure 



* Proc. Roy. Soc., vol. Ixviii., p. 87. 



