418 ELECTRO-PHYSIOLOGY CHAP. 



lower surface of the sartorius, parallel with the fibres of the muscle, 

 and as much extended as possible. Then, under some conditions, 

 the thinnest bundle of muscle -fibres, hardly corresponding in 

 diameter with a frog's sciatic, will suffice, on exciting the trans- 

 verse section, to produce secondary contraction. For the rest, 

 with moderate excitability of nerve, hardly any position fails to 

 produce vigorous secondary contraction of the muscle. Secondary 

 excitation in which the nerve bridges the muscle at right 

 angles, has a special interest. This is easily effected if the 

 sciatic of the leg, fixed on a movable glass plate, is clamped, 

 along with the sacral plexus, to a conveniently fixed glass rod, and 

 applied, after moderate extension, to the inner surface of the 

 dependent sartorius, or simply hung over it. In the latter 

 case the most vigorous secondary contraction is found on making 

 a double transverse section in the sartorius with both ends 

 pendent, or by moistening it in the usual way (Kiihne, 5) ; it 

 then appears that the secondary activity of this most regular 

 muscle, on which du Bois' law of the muscle current can be 

 infallibly demonstrated, is independent of the amplitude of the 

 current of rest to such a degree that there are actually no points 

 or lines on the muscle excited from the cross-section which fail 

 to give secondary action. Even more surprising than secondary 

 excitation with the nerve laid across the primary muscle, is the 

 fact that application to the surface of the transverse section of 

 the muscle does not abolish secondary action, which does not har- 

 monise with the prevailing view of the dependence of secondary 

 excitation upon the muscle current (Kiihne, I.e. p. 24 f.) ; under 

 these conditions, indeed, it might almost be doubted if the wave 

 of electrical variation is really the immediate cause of secondary 

 excitation. Kiihne (I.e. pp. 2737), however, gave a direct proof 

 that it is so, by showing that the part in contact with the 

 secondary nerve did not act at the same moment as that in which 

 the primary excitation impinged on the muscle at another and 

 more remote spot, but as much later as was required by the wave 

 of variation to pass from its point of origin to that at which it is 

 led off. The nerves of two gastrocnemii were laid on the sar- 

 torius at some distance from each other, and the muscle was then 

 excited from one end. The interval between the excitations of 

 the two secondary nerves was always quite evident, and often 

 considerable, although excessively fluctuating. While in the 



