in ELECTRICAL EXCITATION OF MUSCLE 249 



ment of the circular muscle layer. Thus in the thin -walled 

 and usually replete colon of Herbivora, the constriction does not 

 usually include the entire periphery, but only forms a few, or 

 several, deep segmental furrows. 



The effect is very different on reversing the current with 

 kathodic excitation of the intestine. We cannot entirely follow 

 Schillbach, who first investigated the effects of electrical excitation 

 of the intestine, when he speaks in this case briefly of a local 

 contraction, and only sees as an essential difference in the work- 

 ing of the two electrodes that there is an appearance " at the 

 anode of peristaltic waves, particularly in an upward direction," 

 while at the kathode, on the contrary, the contractions are 

 wholly local. For, on the one hand, the appearance of a contrac- 

 tion limited to the seat of direct excitation is very general at the 

 anode also ; while, on the other, it must be admitted that the 

 visible effects of excitation at the seat of the kathode always 

 exhibit a fundamentally distinct character from the effects of 

 excitation at the anode. While the typical circular constriction 

 is never wanting at the anode, and appears similarly at the small 

 intestine, as well as at the colon, or rectum, the manifestations of 

 excitation at the kathode develop very variously both in different 

 species of animals and in different intestinal sections of the same 

 animal. In rabbits, guinea-pigs, and mice, complete constriction 

 of the tube of the intestine occurs at the anode, on closure of the 

 current, while at the kathodic contact the change is scarcely 

 perceptible, and it is only by very exact observation that the 

 formation of a small, fluted thickening can be detected, and, 

 corresponding with it, in its immediate proximity, a flat, dinted 

 constriction of the upper surface. This longitudinal fluting, 

 which is only indicated at the point where the current leaves the 

 intestine of rabbits or guinea-pigs, appears invariably in that of 

 cats or dogs as a crest-like, prominent expansion, parallel with the 

 long axis of the intestinal canal, and, like a scar, producing con- 

 striction of the tract lying immediately around it, so that on that 

 side of the intestinal wall a flat, dinted depression is formed, with 

 the fluting already referred to springing from its centre. These 

 changes also persist during the closure of the current, and only 

 equalise themselves more or less rapidly when the circuit is broken. 

 The manifestations of polar excitation in the different sections of 

 the colon of Herbivores are also interesting the anatomical 



