i.] SUMMARY 19 



try to place myself in the position of a listener, and offer some 

 criticism of what you have just listened to. 



You would find, if you critically compared the lecture with 

 its syllabus, that many points mentioned in the syllabus have not 

 been fairly met by the lecture, that the order of the spoken (and 

 written) description differs from the order of items promised by 

 the syllabus, that points have been talked about of which there is 

 no mention in the syllabus. To which my defence is, that 

 memoranda of a printed paper cannot be placed in the same 

 logical order as the thoughts and comments that arise from 

 experiments in the act of demonstration. And so I have left 

 untouched (for the present) the headings " an excised nerve," 

 " a piece of skin," " a green leaf," " a cut flower," " a stem," in 

 the hope that you may for yourselves realise how these things 

 associate themselves in the mind of any one planning a group of 

 considerations. The reason of such association may perhaps be 

 made plain in the course of these lectures. 



You may have found it rather perplexing to be told at some 

 length that positive means negative, and that negative means 

 positive. Some of you have hitherto been quite satisfied to 

 talk about the negative variation of contracting muscle or of 

 excited nerve. I believe that these expressions are nearly 

 always empty to utterers and hearers alike, and I have deliber- 

 ately tried to disturb your easy acceptance and use of paper 

 language, and put you to the trouble of mentally imaging the 

 facts denoted by the words. The points to be definitely 

 registered from what you have witnessed, are : 



(1) From the muscle experiment : that pari passu with its 

 contraction, its ordinary and indubitable sign of life, an electrical 

 change is proof and measure of its state of life. 



(2) From the eyeball experiment : that we have witnessed 

 an electrical response to luminous stimulation. 



(3) From the ivy leaf: that vegetable as well as animal proto- 

 plasm, while alive, gives an electrical response to mechanical 

 excitation. 



(4) From the seed experiments : that the electrical response 

 to electrical excitation can be utilised as a measure of "vitality." 



