334 PROTOPLASM 



zinc. From this he drew two conclusions — that the production 

 of an electric current is a cause of muscular contraction and that 

 the origin of the current is due to a hfe force within the muscle. 

 The first deduction is correct; the second, not justified. 



That a current of electricity will produce muscular contraction 

 is now a well-known fact. It is also true that electric currents 

 arise in muscles but not in the way in which Galvani thought. 

 What actually took place in Galvani 's experiment was the 

 estabUshing of the essentials of a typical galvanic cell. Strips 

 of copper and zinc in an electrolytic solution produce a current. 

 Galvani supplied the two metals, and the muscle possessed suffi- 

 cient salt and water to play the role of an electrolytic solution. A 

 current was produced, and the muscle contracted. 



This physiological experiment of Galvani's, performed in 

 Bologna in 1789, led Volta of Pavia, in 1800, to put together the 

 kind of electric cell that we now know by his name. The experi- 

 ment of Galvani on muscle contraction was the first in electro- 

 physiology and among the first in dynamic, or galvanic, electricity. 

 The new science of electrophysiology was not put on a sub- 

 stantial basis until fifty years after Galvani, when the German 

 physiologist duBois-Reymond established the fact, which Galvani 

 thought true even though his experiment did not prove it, that 

 organic tissues give rise to electric currents. DuBois-Reymond 

 made the classical observation that if tissue is wounded, there is 

 immediately set up an electric current which flows from the 

 wounded to the nonwounded region. The nature of the wound 

 is immaterial. But it is not necessary to wound an organism in 

 order to produce a current. Tissues constantly maintain differ- 

 ences in potential between each other. Tendon is always negative 

 to muscle, atid root negative to leaf or stem. There thus results 

 a flow of current {i.e., of electrons) from tendon to muscle and 

 from root to leaf if the two tissues are connected by a conductor. 

 Within the body, the salt solutions of the tissues may possibly 

 serve as a conductor (pages 344-345). That electric forces are 

 involved not only in muscular action but in many if not all physi- 

 ological processes seems very Hkely. Michaud has shown that 

 merely touching a gel causes a difference in electric potential, 

 which can be measured. If this is true of nonhving gels, it 

 should be true of Hving gels, such as muscle, nerve, and proto- 

 plasm in general. 



