in ELECTRICAL EXCITATION OF MUSCLE 309 



action " due to latent make excitation at the anode ; and the fact 

 itself is directly demonstrable by corresponding experiments on 

 other infusoria less resistant to the action of current than Para- 

 nuecium aurelia. On Parama?cium bursaria (the galvanotropic 

 reaction of which to weak currents is as well marked as is that 

 of ParaniRBcium aurelia), Yerworn, using strong currents, suc- 

 ceeded, as in the case of the above-mentioned rhizopods, in 

 producing a visible destruction of one pole of the body, i.e. of the 

 anodic pole, that is posterior when swimming takes place. At 

 closure of the current the first effect is as usual an axial orienta- 

 tion, and subserviently as the proteid begins to swim over towards 

 the kathode, a hyaline mass protrudes from the posterior end and 

 gradually enlarges. It can hardly be doubted that this is analo- 

 gous to the anodic disintegration that occurs in Actinospha?rium 

 and Pelomyxa. It is still easier to bring about a similar reaction 

 in the case of Bursaria trunculata ; moderately strong currents 

 are sufficient to effect a granular disintegration of the anodic end 

 of the body, which increases as long as the circuit remains closed, 

 until the whole animal is converted into a granular mass loosely 

 held together by glutinous material. These large and more 

 resistant infusoria have no time to adjust their axis, especially 

 with strong currents, but the destruction begins at any aspect of 

 the body which happens to be turned towards the anode at the 

 moment of closure (Verworn). 



A large number of other ciliated Infusoria, also some of the 

 Flagellata (Peridinium tabulatum and Trachelomonas hispida), as 

 investigated by Verworn, behave in a similar manner. On the 

 other hand, in some other protozoa, the current produces a 

 precisely opposite directive effect. If the swimming or crawling 

 movements towards the kathode be designated as negative gal- 

 vanotropism, the reverse effect (anterior end to anode, and 

 movement in that direction) may be called positive galvanotropism. 

 A'erworn found this last-named effect in Opalina ranarum, also in 

 certain Flagellata, Polytoma uvella and Cryptornonas erosa in 

 particular. The phenomenon described by Verworn as " transverse 

 galvanotropism " is, moreover, remarkable ; certain very elongated 

 .Infusoria (e.g. Spirostomum anibiguinn., 2 mm. long) place them- 

 selves with their long axis at right angles to the lines of current 

 (perhaps in consequence of a failure of excitation by transverse 

 currents). Apart from these isolated cases, which require further 



