Xll PREFACE. 



state (the former being indicated galvanoscopically by the pre- 

 sence in the tissue of a current from the excited to the unexcited 

 part, and mechanically by the presence of more or less spasm, 

 the latter by the opposite effects), but that muscle varies in 

 the direction of greater or in that of less fitness for func- 

 tional activity. By employing such terms as 'up' or 'down' 

 to denote these two tendencies, it is possible to express his 

 conception thus : A voltaic current produces at the anode 

 when it is closed an ' up ' state, of which the galvanoscopic 

 sign would be relatively positive, and the mechanical sign 

 axial extension but aptness to contract ; at the cathode a 

 ' down ' state, associated conversely with * negativity,' and axial 

 shortening. The assumption of a state intermediate between 

 these two is suggested by the indications of what, for want 

 of a better name, is called by Biedermann ' reaction,' that is, 

 of a tendency (of which the behaviour of all excitable tissues 

 suggests the existence) to assume a condition opposite to that in 

 which it actually is, by virtue of which the * down ' state is 

 produced at the anode at make, the * up ' state by the cathode 

 at break. In Biedermann's experiments it was strikingly seen 

 that the same external cause produces contraction and negativity 

 when acting on muscle in the ' up ' state, relaxation and posi- 

 tivity when acting on the same muscle in the ' down ' state. 

 This being so, there may be between contraction and complete 

 relaxation an intermediate state in which the two opposite 

 tendencies neutralise one another. If such a state exists, it does 

 not follow that it is the normal state of the tissue, for by the 

 word normal the physiologist understands simply the state 

 which best fits the structure for its function, and cannot be 

 guided in his use of it by the correlation of its elementary 

 properties. 



Part III contains Prof, du Bois-Reymond's investigations in a 

 field of research in which up to the present moment he has been 

 almost the only worker that of the electrical phenomena of fish 

 which are possessed of special electrical apparatus. The Memoir 

 on Malapterurus, which appeared a few years ago in the Author's 



