416 GENERAL PHYSIOLOGY 



discovered, was Kiihne's observation recalled and confirmed by 

 means of more complete methods. The examination of a long 

 series of free-living cells followed, all of which follow a law of 

 polar excitation differing in various ways from that of nerve and 

 muscle. 1 



The best method of employing galvanic stimulation with non- 

 polarisable electrodes upon a slide under the microscope, is to use 

 a slide (Fig. 197) upon which two strips of porous clay, such as is 

 used in the porous cups of the galvanic element, are cemented 

 parallel to one another (a, a^) ; the ends of these strips are united 

 by a wall of insulating cement (colophonium and wax) (b, Z^) ; thus 

 a small open box is formed, in which can be placed a drop of water 

 containing the objects to be investigated. The brushes of ordinary 

 non-polarisable electrodes are laid upon the two parallel strips. It 

 is possible by means of this small contrivance to send nearly 

 parallel currents through the microscopic objects, and, at the same 



FIG. 197. Slide bearing a small box for the galvanic stimulation of microscopic objects, a, 01, 

 Strips of fired clay ; b, bi, insulating walls of cement, which with the strips form a box, in 

 which the objects are placed. 



time, to observe the effects of the stimulation under the microscope. 

 If Actinosphcerium be stimulated by a constant current in this way, 

 when it has protruded its pseudopodia from its spherical body, 

 like the rays of the sun, it is found that, at the moment of 

 making, phenomena of contraction may be observed in the pseudo- 

 podia that are extended in the direction of the anode and the 

 kathode, the protoplasm coming together into small globules and 

 spindles and streaming toward the body (Fig. 198). The pseudo- 

 podia that are extended perpendicularly to the direction of the 

 current remain at rest. Hence, at the moment of closing there 

 is both an anodic and a kathodic excitation of contraction. 

 The excitation at the anode is the stronger of the two. Through- 

 out the duration of the constant current the following is notice- 

 able : At the kathode after the making, the phenomena of excitation 

 gradually disappear, and the pseudopodia there assume their former 

 smooth appearance, while upon the side of the anode the excitation 



Cf. Verworn ('89, 2, 3). 



