PROFESSOR AT KONIGSBERG 103 



electrical moment of the surface : he thus succeeds in reducing 

 problems of current distribution to a question of the potential 

 of electrical surfaces and bodies. Lastly, with the aid of 

 Green's propositions, he develops the theorem communicated 

 in January to du Bois-Reymond of the equal mutual action of 

 two electromotive surface-elements, and thus clears the way 

 for the experimental confirmation of the law and its important 

 applications. For since each single element of an electromotive 

 surface discharges as much electricity into a galvanometer 

 circuit as would flow through itself if its e. m. f. were situated 

 in the galvanometer circuit, the total effect of all the electro- 

 motive surface-elements must be equal to the whole current 

 passing through the galvanometer. In all experiments on animal 

 electricity, in which nerve and muscle represent extended 

 material conductors, with electromotive forces distributed in 

 them, it now becomes possible to test and correct the theo- 

 retical conclusions of du Bois-Reymond and other physiologists 

 as to arrangement of electromotive elements within the 

 nerve or muscle, by means of laws that have been ascertained 

 empirically. 



Meantime, the interest of the various medical and literary 

 circles in Konigsberg had been aroused by the effect of 

 Helmholtz's Physiological Theory of Colour upon the scientific 

 world ; and he responded to their inquiries by giving a lecture 

 on 'Goethe's Scientific Researches', delivered on January 18 

 (Coronation Day) to the Deutsche Gesellschaft. 



Helmholtz had been induced by various considerations to 

 protest against the attack made by Goethe upon the optical 

 work of Newton, and he accordingly desired, in order to avert 

 misunderstanding, to show that although Goethe's physical 

 conclusions were often erroneous, he had done indisputable 

 service in botany and osteology, and must always be reckoned 

 among the great men of science. In his Sketch of a General 

 Introduction to Comparative Anatomy^ Goethe expresses the 

 idea (which was never better nor more clearly stated, and 

 has subsequently been but little altered) that all differences 

 in the structure of animal species must be looked upon as 

 variations of a common type, brought about by the coalescence, 

 alteration, increase, atrophy or total loss of single parts. A 

 similar analogy between the different parts of one and the 



