PROFESSOR AT KONIGSBERG 89 



of time-measurement previously described in Part I by which 

 a contracting muscle records the magnitude of its twitch upon 

 a travelling surface to find a simpler method of confirming his 

 determination of the rate of nervous transmission. After Ludwig, 

 with the kymograph, had succeeded in recording the variations 

 of blood-pressure in the vessels of a living animal, Helmholtz 

 constructed his myograph for the graphic record of the con- 

 traction of a muscle its principle being that a lever lifted 

 by the twitching muscle traces a curve upon a surface moving 

 at uniform speed, the vertical co-ordinates of which are pro- 

 portional to the shortening of the muscle, the horizontal to 

 the time. If two curves are recorded one after the other in 

 such a way that the writing-point is always at the same place 

 on the travelling surface at the moment of excitation, then both 

 curves will start from the same point, and it can be seen from 

 their congruence or non-congruence whether the different 

 stages of the mechanical response of the muscle occur in both 

 cases at the same interval after excitation. Two years later 

 Helmholtz published important additions to these experiments 

 on the frog, as recorded with the myograph. 



Simultaneously with the above he published in the Kieler 

 Monatsschrift, for April, 1852, the essay previously announced 

 to du Bois on the ' Results of Recent Researches in Animal 

 Electricity'. He gave a masterly sketch of the development 

 of nerve physiology, and described the interest attaching to 

 the 'investigation into the nature of the mysterious agent 

 which, acting along barely visible nerve-threads, produces 

 such fine gradations, such mighty energies, such complicated 

 exchanges of sensation and motion an agent that is the first 

 link in the chain of processes which connect the mind that 

 feels and wills with the material outer world, enabling it to 

 receive and give out impressions '. As early as 1743 the Leipzig 

 mathematician Hausen had expressed the opinion that this 

 agent might be identical with electricity. Helmholtz now ex- 

 pounded the opposite theories of Galvani and Volta, the first 

 of whom regarded animal electricity as the source of the 

 electrical phenomena in all his experiments, while the latter 

 by his theory of contact electricity, which led him to the most 

 brilliant discoveries, had pushed the experiments relating to 

 animal electricity proper completely into the background. He 



