in ELECTRICAL EXCITATION OF MUSCLE 237 



surface is brought into contact with the kathode, a small lono;i- 



o * Q 



tiulinal swelling springs up under the point of the electrode as 

 soon as the current is made, its long axis lying perpendicular 

 with the course of fibres in the muscular bundle excited. The 

 whole manifestation is indisputably the same, in a less degree, as 

 the persistent kathodic contraction when a longitudinal muscle- 

 band is excited. 



In both cases there is the striking demarcation of the swell- 

 ing, as well as the inconspicuous total contraction of the muscle, 

 due to local excitation. In contrast with this, the total contrac- 

 tion of the ring-muscles is very marked with unipolar stimulation 

 from the anode. Careful gradation of current and a fine-pointed 

 brush electrode are essential in order fully to determine the con- 

 trast of excitation effects in circular and longitudinal muscles in 

 this case also. If a single bundle of circular fibres is excited in 

 the middle, between two longitudinal muscle-bands, the most 

 striking appearance on closing the current is the formation of a 

 furrow running parallel with the direction of the fibres, the 

 origin of which is easy to explain from the sharp contraction of 

 the excited fibres. "With artificial enlargement, it is easy to see 

 that the muscle-fibres immediately under the point of the anode 

 do not take part in the contraction, but (as in longitudinal 

 muscle under corresponding conditions), a more or less well- 

 marked canal is formed, running transversely to the fibres, at 

 either side of which the muscle-bundle shortens. Sometimes 

 the transverse swellings which mark off the canal on either side 

 stand out quite clearly ; yet it always requires close observation 

 In detect an appearance, which is obvious when the longitudinal 

 muscles are excited. While in the latter, with anodic excitation, 

 total contraction tends to disappear in favour of local changes of 

 fiirm owing to the great length of the muscle-bands, the exact 

 Apposite occurs in the small short bundles of circular fibres, in 

 which the total effect is more striking than the local changes. 

 This is best studied at points where, from the contraction of the 

 surrounding parts and consequent folding over of the membrane, 

 or from pronounced total relaxation, individual parts stand out 

 in a blister. If contact is made with the anode at such a 

 part, where the circular fibres appear curved convexly outwards, 

 closure at once produces a segmental constriction, parallel with 

 the fibres, and recalling the similar effect produced under analogous 



