170 SECONDARY ELECTROMOTIVE PHENOMENA IN 



researches by which I sought to elucidate the secondary electro- 

 motive phenomena in muscles and nerves. Though the pursuit of 

 my chief object was excessively hindered by these preliminary 

 studies, yet my impatience was moderated, not only by the evident 

 necessity of laying a firm foundation to work upon in this depart- 

 ment, but also by the consideration that this foundation is equally 

 indispensable for all electro-physiological investigations 1 . 



I was unfortunately prevented by other problems for nearly 

 twenty years from making use of what I had ascertained. Almost 

 at the same time that I became possessed of unpolarisable elec- 

 trodes, I had discovered in saline clay an invaluable means of 

 leading currents in or off in electro-physiological experiments, I had 

 given Poggendorff's method of compensation the right form, and 

 somewhat later I added to these advances in methods of research, 

 the invention of the aperiodic galvanometer. It thus became 

 necessary for me to repeat almost all my former experiments with 

 these new and much better appliances, in which measurement of the 

 electromotive force now took the place of mere estimation of the 

 strength of the current. The investigation of the living specimens 

 of Malapterurus from West Africa which were kindly consigned to 

 me by Professor Goodsir of Edinburgh, also took me away from this 

 subject ; and, more recently, it has taken me nearly two years to 

 work up the posthumous papers of Dr. Sachs on Gymnotus. The 

 latter interruptions had, however, the important result that I gained 

 some information regarding secondary electromotive phenomena in 

 electrical organs. 



6. Preliminary description of Apparatus and Methods. 



I defer the detailed description of the apparatus and methods 

 which I now use until I have further communications to make. 

 It is, however, desirable to say sufficient on the subject to render 

 what follows intelligible. In the experiments on muscles the 

 gracilis and semi-membranosus muscles of the frog were commonly 

 used. They were left in their natural connection, and extended 

 in the ' muscle-stretcher 2 ,' in the way I have employed whenever I 

 desired to work with muscles in an immobilised state. Close 

 to the ivory plates of the stretcher the edges of the wedge-shaped 



1 Cf. Gesammelte Abhandlungen, vol. ii. pp. 191 ff. 



2 Untersuchungen, vol. ii. part i. p. 86. Also Gesammelte Abhandlungen, vol. i. 

 pp. ii 8, 119, and vol. ii. p. 313. 



