x ELECTROMOTIVE ACTION IN NERVE 333 



contrary effect appears when current leaves the heart by the 

 brush-electrode. If closure occurs at the beginning of the general 

 diastole, a new systole will at once appear at the point of exit 

 (Jcufhodic closure contraction}. 



" If the current is left undisturbed for some time in this 

 last direction, and is then opened during a general diastole, the 

 wall of the heart near the brush-electrode will not take part in 

 the ensuing systole, owing to the marked autonomous up change ; 

 it remains diastolically relaxed, and the systolic pressure of the 

 blood causes the relaxed point to swell out considerably. This 

 is the kathodic opening inhibition, which thus expresses itself in 

 precisely the same way as the anodic closure inhibition above 

 described, and cannot be viewed as a mere fatigue effect. If, on 

 the contrary, current enters the wall of the heart for a prolonged 

 period by the brush-electrode, a contraction appears immediately 

 after it is broken, in the proximity of its point of exit. This 

 contraction may even be more pronounced than the natural sys- 

 tolic contraction, as appears externally from the paler colouring 

 of the heart-wall. This is the anodic opening contraction derived 

 from autonomous descending alteration, the analogue of the 

 kathodic closure contraction described above, which depends upon 

 allonomous descending alteration. 



" The anodic opening contraction and kathodic opening 

 relaxation are fundamentally analogous with the phenomena of 

 successive contrast, as observed in other living substances, and 

 are as little as these to be referred to a mere fatigue effect." 



In contrast with this straightforward exposition, the " modified " 

 molecular theory recently (in 1888) advanced by Bernstein (52) 

 is unsatisfactory, in spite of its elaborate detail. It starts, more- 

 over, with certain postulates that are, at least, doubtful. In 

 the first place, it is held necessary to conceive the living fibres (in 

 muscle and nerve) as consisting of longitudinal series of mole- 

 cules, looped together at the natural transverse section of the 

 muscle (tendon-end), and " polarisable in the fluid which contains 

 them," although, on account of their close juxtaposition longitudin- 

 ally, such polarisation can only take place " at the free surface " 

 of the row of molecules. By this hypothesis (which he believes 

 to be confirmed by the inexcitability of the artificial cross-section 

 of a muscle to current), Bernstein explains the inexcitability of 

 the tissues in question to transverse passage of current, since it 



