252 ELECTRO-PHYSIOLOGY CHAP. 



muscles discharged at the anode. But just as the propagation 

 of a localised excitation in the muscle of the intestine depends 

 upon different, and so far not exactly determined, data, so too 

 with polar effects of excitation. On the one hand, a high 

 excitability of the excitable parts is apparently essential, while 

 on the other, the nervous mechanism of the intestine itself seems 

 again to play a very important part in the bringing about 

 of progressive contraction. Most authors incline to the view 

 that both the normal and the artificially excited peristalsis are 

 caused solely and invariably by the intestinal nervous system 

 (Nothnagel, Llideritz, 33). Without taking a definite position 

 in this question, which was discussed above, the possibility of 

 propagating the excitation effects discharged at the poles of 

 the constant current may be suggested. With the application of 

 strong currents Liideritz observed this at the positive as well as 

 at the negative pole ; but the kathode seemed to produce a 

 stronger effect than the anode. " In the rabbit and guinea-pig 

 this effect appeared in well-marked cases as a contraction of the 

 longitudinal muscle of the intestine, extending for several cms., 

 upwards and downwards, from the electrode, accompanied by a 

 contraction of the circular muscles running exclusively, or chiefly, 

 in the direction of the pylorus ; in the cat the contraction of the 

 circular muscles may run upwards and downwards, or in the 

 direction of the pylorus" (33, p. 14). 



In contrast with these uncertain, and still unexplained, 

 data, the effects of electrical excitation of the ureter are 

 characterised as well by the certainty of their appearance 

 as by their great regularity. The thorough investigations 

 of Engelmann showed that apart from the slowness of the 

 reactions there is complete conformity with regard to the 

 polar manifestations of excitation, between the ureter and 

 striated skeletal muscle, so that these observations give cogent 

 support to the theory of the unlimited applicability of the law of 

 polar excitation. It is, therefore, at first sight the more sur- 

 prising that, so long as the ureter remains in situ, the effects of 

 electrical excitation with the constant current are diametrically 

 opposite to what might be expected from Engelmann's investiga- 

 tions. On applying unpolarisable electrodes to two points along 

 the rabbit's ureter, after exposing it with the utmost care and avoid- 

 ance of unnecessary cooling, Engelmann found with closure of the 



