PHENOMENA OF MUSCLE. 247 



That weak positive anodic polarisation can be obtained by passing 

 excessively strong- currents through a destroyed spot into the 

 muscle, is on obvious grounds not to be doubted ; but weak break- 

 contractions are also obtained under those circumstances. 



Negative kathodic polarisation becomes almost impossible when 

 the point of exit of the current is killed, provided that its strength 

 and duration are not too great. 



Experiments in which the electrodes are applied to the surface of 

 the muscle have the disadvantage, that the strength of the polarisation 

 phenomena, with equal strength of stimulating current, must de- 

 pend on the extent of surface of contact of the electrodes. For it is 

 this which determines the density with which the current enters or 

 leaves the muscle, and on this density the strength of anodic and 

 kathodic polarisation depends. Even if the density of the current is 

 equal throughout the intrapolar tract, i.e. the tract in which the 

 fibres are parallel, yet it may be different at the spot of entry or 

 exit, and at the same time the strength of the polarisation-current 

 may be very different, whereby the measurement of the intensity 

 of the stimulating current loses much in value. It is also of 

 no little importance, as has already been explained above, that the 

 current enters the fibres cross-wise or obliquely, and that nearly all 

 the fibres are traversed by portions of current, and therefore have 

 both anodic and kathodic spots. 



Tschiriew x has of late given an account of experiments made with 

 the sartorius. in the results of which he sees confirmation of du Bois- 

 Reymond's theory. He laid both stimulating electrodes on one sur- 

 face of the muscle, both galvanometer electrodes (Fleischl's brush 

 electrodes) exactly opposite them on the other surface, so that the 

 intrapolar tract amounted to about 15 mm. He obtained, * with 

 short periods of closure of the polarising current up to 4 sees, 

 and sometimes more and with the freshest possible preparations, 

 purely positive excursions of the needle. With a longer closing 

 time, and when from the duration of the experiment the ex- 

 citability of the preparation had decreased, the excursions became 

 diphasic, a negative deflection preceded the positive, and finally 

 a purely negative polarisation remained.' As appears from a table 

 of experiments, Tschiriew changed the direction of the current 

 from one experiment to another in the same series 2 . The change 

 in the direction of the current made the spot of the muscle 



1 Archiv f. Anat. u. Physiol. 1883. Festschrift, Suppl. Vol. p. 284. 



2 The explanation of his results follows naturally from what I have already said. 



