304 ELECTRO-PHYSIOLOGY CHAP. 



such pseuclopodia as lay across the lines of current. Vervvorn 

 was unable to detect any definite kathodic break effect. 



The excitation changes that are observable under similar 

 conditions in Pelomyxa palustris are of no less interest. Pelomyxa 

 is a solid mass of naked protoplasm, often as much as 2 mm. in 

 size, which is rendered very opaque by the large quantity of sand 

 and mud englobed by the animal. The movements are extremely 

 sluggish, and, as in many Amoeba?, consist in a now of the enclo- 

 plasm along the body-axis in a given direction, with a bending 

 round and backward now along both sides. In this way a blunt 

 process in the direction of the axial current is formed, at the 

 margin of which a hyaline border is often distinguishable. Ex- 

 citation produces a variety of effects according as it involves the 

 entire surface, or is localised to one spot, and is strong or weak. 

 " Weak prolonged stimuli acting upon the whole body, e.g. vibra- 

 tions, produce a very gradual but complete balling of the body. 

 Weak localised stimuli produce a gradual withdrawal of the ex- 

 cited part. Strong stimuli (e.g. by chemical reagents) acting 

 upon the body likewise produce a spherical rounding, while at 

 the same time there is an escape of the granular endoplasm, 

 in consequence of the disintegration of the outer protoplasmic coat 

 this escape is partial with localised excitation. The granulated, 

 disintegrating protoplasm bursts out, and the appearance is the 

 same as when Actinospruerium is submitted to the action of strong 

 currents." A sufficiently strong galvanic current acts upon Pelo- 

 myxa with the same results (Fig. 98). 



At closure the contents of the body burst forth on the 

 anodic side, and as in Actinospruerium, the disintegration spreads 

 more and more in the direction of the kathode, until the last 

 trace of protoplasm has disappeared. This process of disintegra- 

 tion passes with diminishing rapidity from the anode to the 

 kathode in about ^ to |- minute, with currents of equal efficacy, 

 at the end of which period the individual is completely abolished. 

 At first the process is extremely sudden, then slower, until it 

 gradually becomes imperceptible. It passes over the whole body 

 in the form of an annular constriction, starting from the anode 

 and advancing towards the kathode ; that portion of the body- 

 mass which is on the anodic side of the constriction, i.e. which 

 lias been traversed by it, is in a state of granular disintegration; 

 that portion which is on the kathodic side is still normal and 



