20 THE GENERAL CHARACTERS OF CELLS, BY S. STRICKER. 



even when the pressure upon them prevents any increase in thickness. 

 It is evident from this experiment that protoplasm is an elastic body, 

 since it contracts when the extending force is removed. The contrac- 

 tion, however, appears to correspond here with the elasticity of the 

 irritated substance, because a shortening occurs which is not maintained. 

 An additional argument in favour of this view is, that the experiment is 

 more successful when it is tried a second or third time. The corpuscles 

 then contract much more energetically than at first. 



c. ELECTRICAL STIMULI. The action of electric currents on 

 protoplasm is very variable. 



The excitation of amoeboid movements by means of weak 

 induction currents has, up to the present time, only been ob- 

 served by Kiihne in amoebse, and by Golubew in certain white 

 corpuscles of the blood of the frog. 



Kiihne* saw amoebae assume a spheroidal form, when made 

 to form part of a constant current; whilst, after exposure 

 to an intermittent current, the stellate corpuscles of the cor- 

 nea became fusiform, and then reassumed their original 

 shape. 



Golubewf states, from experiments made in Kollett's labo- 

 ratory, that after being repeatedly irritated the cells become 

 flattened, but even in that state exhibit changes of form. If 

 stronger stimuli are applied to them in this condition, the disc- 

 like mass again contracts and becomes spheroidal. He further 

 observes that the fusiform colourless cells of the blood of the 

 frog, which present no spontaneous movements, when mode- 

 rately irritated, contract to spheroidal masses, but soon again 

 revert to their original shape. IJ have observed contractions 

 and dilatations to take place in embryonal capillary vessels after 

 the action of induction currents. 



Kiihne has observed the following law of contraction in the 

 protoplasm of Actinophrys eichhornii during the action of a 

 constant current : 



* Loc. cit. 



f Wiener Sitzungsberichte, 1868. 

 | Wiener Sitzungslerichte, 1866. 

 $ Loc. cit. 



