134 J- F. MCCLENDOX. 



ments would elongate the muscle. And even though contraction 

 were produced by inequality in surface tension, as assumed by 

 Macallum 1 the total surface change would be so small as not to 

 account for the energy liberated in contraction. In order to 

 avoid this last difficulty Bernstein made use of hypothetical 

 ellipsoids. These were surrounded by elastic material to account 

 for elongation of the muscle. 2 



The great differences of potential (several hundred volts) that 

 may be produced by the electric organs of fish, is achieved by 

 the arrangement of the modified muscle plates in series. All of 

 the plates have the nerve termination on the same side. On 

 stimulation of the nerve, each plate becomes negative, first on 

 the nerve termination side, and thus the negative side of one 

 plate touches the positive side of the next plate. In this way 

 the direction of the current may be determined by studying the 

 anatomy of the innervation. This rule, discovered by Pacini, 

 finds an exception only in Mahpterurus, whose electric organ 

 is supposed by Fritsch to be derived, not from muscle but Irom 

 skin glands. 



The electric fish are relatively immune to electric currents 

 passed through the medium. This is not merely an apparent 

 immunity due to the fish being out of the path of the current, or 

 the current being short circuited by sea water (in case of marine 

 fish). I have received severe shocks from a torpedo that was 

 entirely submerged in sea water. 



3. Amoeboid Movement. 3 



The normal unstimulated surface of plant and animal tissues 

 is electro-positive in relation to the cut or injured surface of 

 the cells. We have given reasons for assuming that this indicates 

 greater permeability of the plasma membrane to kations than to 

 anions, the latter accumulating in the cell interior, gives it a 

 negative charge. 



There are two reasons for believing that this is true also of ihe 

 Amoeba: 



1 Science, n. s., 1910, XXXII.. 822. 



2 Meigs., Am. Jour. Physiol., 1910, XXVI., 191, supposes the rounding up of 

 muscle elements due to increased turgor. 



3 McClendon, Arch. f. d. ges. Physiol., 1911, CXL., 271. 



