302 ELECTRO-PHYSIOLOGY CHAP. 



markable and in many respects important reactions of Actino- 

 sphserium to the galvanic current. We shall in the main follow 

 the account given by Verworn (I.e.} who has recently repeated 

 these observations, completing and extending them in various 

 directions. In regard to method it should be observed that un- 

 polarisable electrodes were exclusively employed in these experi- 

 ments. The Actinosphseiium is placed in a few drops of water 

 in a little excitation chamber, made by cementing two slabs of 

 porous clay, joined by two transverse partitions of cement, on to 

 a large object glass, so as to form a (closed) rectangular space, to 

 the clay sides of which brush electrodes were applied, so that 

 current could traverse the chamber in approximately parallel 

 lines. In consequence of the high resistance in the circuit, com- 

 paratively high electromotive force must be used in order to 

 obtain distinct effects, which, however, in such cases are perfectly 

 characteristic. At closure of the current, in the first place, the 

 pseudopodia, both on the anodic and kathodic side of the globular 

 body, become varicose, and begin to contract as described above ; 

 lohereas the pseudopods that are situated at right angles to the line 

 of current exhibit no changes. On the kathodic side the effects of 

 excitation are comparatively inconsiderable and very evanescent ; 

 the pseudopodia soon resume their normal aspect. The corrc- 

 srjonding effects on the anodic side, on the contrary, proceed unin- 

 terruptedly as long as the current is passing. Little by little the 

 pseudopodia are completely withdrawn ; the vacuoles in the 

 cortical layer begin to collapse and empty themselves of fluid ; 

 a gradual dissolution of the body -mass takes place on the 

 anodic side, while the protoplasm disintegrates into granules. In 

 this manner a concave gap is gradually formed on the anodic side, 

 while a very slow retractation of pseudopods is taking place over 

 all the rest of the body. Finally, the Actinospha_ j rium becomes 

 sickle-shaped like a new moon, the greater part of the body-mass 

 having undergone disintegration into granules (Fig. 97). 



If the circuit is opened at a moment when the pseudopodia are 

 still in a normal state, except on the anodic side, the corrosion at 

 the anode ceases directly, and the pseudopods on the kathodic 

 side become varicose in about the same degree as had taken place 

 immediately after the closure of the circuit. This effect is, how- 

 ever, very evanescent ; the pseudopods soon recover their normal 

 aspect, while the anodic gap gradually fills up at the same time, 



