336 ELECTRO-PHYSIOLOGY CHAP. 



At break " there is a sudden depolarisation, whereupon the positive 

 ion at the kathode disappears. The firmer combination of intra- 

 molecular oxygen suddenly breaks down, and as the molecule 

 had during the passage of the current collected an over-charge 

 of the same, which it is no longer able to hold, this portion is 

 liberated, and causes a rupture of the molecule, co-significant with 

 excitation." Without going more closely into details of the 

 explanation of opening tetanus, and the modifications of excita- 

 bility at break, it may be stated that on this theory the in- 

 efficacy of transverse passage of current is explained as meaning 

 " that the positive ion locks each excitable molecule in the same 

 degree in which the negative ion slackens it. The liberated 

 negative ion is therefore unable to combine with the oxidisable 

 groups of atoms of the molecule, and remains stationary." This is 

 not the place to enter further into Bernstein's elaborate account of 

 the possible constitution of his hypothetical molecules. He sup- 

 poses them to consist of N-containing nuclei, longitudinally linked 

 with atoms of 0, while the free superficies is set with oxidisable 

 groups of atoms that are rich in C and free of 1ST. These last 

 react towards the nucleus as electro-positive charges, while the 

 " assimilated " combining appears at the artificial cross-section 

 as the electro-negative charge of the nucleus (cf. Fig. 111). The 

 ions of molecules are not therefore polarisable in the previous 

 sense, " but are already, in their normal state, charged with certain 

 ions, as though polarised by a foreign current." We have else- 

 where shown that Bernstein tries to explain all galvanic mani- 

 festations in nerve and muscle by this " electro-chemical molecular 

 theory." Yet it may be doubted whether these profound specula- 

 tions as to the structure of the molecules, and the constitution of 

 living matter, are a better foundation for a comprehensive theory 

 of the correlative manifestations than the straightforward 

 propositions which Hering derives solely from facts, and from 

 the fundamental laws of metabolism. And as Bernstein 

 remarked of du Bois-Eeymond's molecular theory, that it gave 

 no further outlook on the mechanical and electrical sides, unless 

 a very one-sided view of the constitution of living matter were 

 adopted, so many will not fail to say the same of his own " electro- 

 chemical molecular theory." 



In conclusion, a word must be said as to the prevailing 

 theories of the nature of conductivity of excitation, in which, as 



