298 ELECTRO-PHYSIOLOGY CHAP. 



We have seen that, contrary to the behaviour of the ureter 

 as observed by Engelmann, the conductivity of striated muscle 

 (sartorius) exhibits no perceptible diminution under the influence 

 of the anode. This is the more striking since there is complete 

 agreement in both cases as regards direct excitability. And it is 

 further less likely that there should be any fundamental diverg- 

 ence between the two cases, since anodic inhibition of conduct- 

 ivity is very pronounced in nerve also. The difference must be 

 due simply to external factors, among which may be instanced the 

 thickness of muscle and transverse course of the lines of current. 

 The fact above alluded to, that kathodic inexcitable points may 

 be so modified by the influence of the anode as to become capable 

 of excitation once more as soon as the electrical current leaves 

 the muscle at the points in question, only show that they have 

 again become sensitive to direct electrical excitation. But since 

 we may conclude from this that alterations of muscular excit- 

 ability by no means invariably entail corresponding alterations of 

 conductivity, it is conceivable that, notwithstanding the restora- 

 tion of direct excitability, the power of conduction, i.e. of being- 

 thrown into excitation indirectly by a wave of contraction from 

 some other point, may sometimes be permanently abolished at the 

 kathode. Experiments with passage of current through one half 

 of a curarised sartorius indicate, however, an opposite result, i.e. 

 even in cases where polarisation has been so long continued that 

 there can be no question of spontaneous restoration of the now 

 incapable muscle section, the power of propagating the excitatory 

 process has been invariably and even permanently restored under 

 the influence of the anode, provided the current used be suffi- 

 ciently powerful. 



In this way it lies in our power to render any given section 

 of a muscle with parallel fibres permeable or impermeable to a 

 wave of contraction from without, according as we make the 

 current traversing one half of the muscle enter, or pass out, at the 

 centre of the muscle. 



As regards alterations of excitability in a polarised muscle, 

 \\e have direct proof that whether extra- or intrapolar they do 

 not extend beyond the physiological kathode or anode, and there 

 is no reason to infer the opposite for alterations of conductivity. 

 All the evidence, on the contrary, goes to show that the one as well 

 as the other must be regarded strictly as a polar effect of current. 



