Sir John Scott Burdon-Sanderson, Bart. 



XI 



gross ones, so compounded with incidental effects that it is difficult or 

 impossible to discriminate the finer details of the fundamental active 

 alteration. 



One type of physico-chemical change, however, appeared to him to 

 approach more closely than others to that which is assumed to take place in 

 the actively responding excitable tissue ; this type is that alteration of 

 electrical state which du Bois-Eeymond had shown to be recognisable in 

 nerve and which had long been known to occur in muscles and notably in 

 the electrical organs of fishes. Acting on this view, Burdon-Sanderson 

 commenced his well-known researches into the characters of the electro- 

 motive phenomena displayed by excitable tissues, and the investigations thus 

 started were destined to occupy him for the remainder of his life, that is for a 

 period of thirty-five years. They form Burdon-Sanderson's most noteworthy 

 contribution to physiological knowledge and illustrate in a striking way the 

 pertinacity with which he investigated a difficult physiological problem and 

 the necessity which he felt for utilising in such investigation recording 

 instruments of the utmost precision. Examples of the latter characteristic 

 are the time and labour which he devoted to devising suitable modifications 

 of the repeating rheotome for use with the galvanometer, and to perfecting 

 the employment for physiological purposes of Lippman's capillary electro- 

 meter. 



For some time the attention of Darwin had been directed to the 

 phenomena of insectivorous plants, especially his " beloved Drosera : a 

 wonderful plant or, rather, a most sagacious animal." Darwin's work on the 

 digestive powers of Drosera brought him into communication with Burdon- 

 Sanderson, and a letter written in July, 1873, shows that Darwin was struck 

 with the notion that the excitable cells of the plant might exhibit phenomena 

 in all essentials similar to those present in excitable animal tissues. Drosera 

 led to Dionsea, which is characterised by the rapid character of the move- 

 ment of its leaf lobes when certain hairs upon their inner surface are 

 touched. The exquisite sensibility of the hairs to mechanical displacement 

 and the extraordinarily rapid character of the mechanical alteration in the 

 leaf attracted the attention of Burdon-Sanderson, who saw in this plant an 

 organ admirably fitted for the investigation of fundamental phenomena. 



He therefore, about 1875, commenced an investigation as to the changes 

 which were associated with this active process and the conditions which 

 influenced their production and character. In the course of this inquiry he 

 discovered that there was a pronounced electromotive change in the leaf 

 every time it passed into the active state. He then devised an ingenious 

 method for keeping the leaves forcibly open by fixation in plaster of Paris, 

 and demonstrated that although no mechanical movement could now take 

 place when an excitable hair was touched, yet each local stimulus of this 

 kind still evoked an excitatory response, since the same active electromotive 

 change was observed. This active " electrical response " was of considerable 

 magnitude, although of comparatively short duration, and its peculiar interest 



