PROFESSOR AT HEIDELBERG 269 



sufferer), he discovered pathogenic vegetable germs in the 

 mucous membrane of the nose, and successfully combated them 

 with quinine, at a time when, as du Bois observes, there was as 

 yet hardly any question of antisepsis. 



By the beginning of 1869 it was obvious that a third edition 

 of Sensations of Tone was wanted. It appeared in the follow- 

 ing year with considerable alterations. Helmholtz not only 

 remodelled the sections on the history of music, and connected 

 them together more closely, but, on the strength of recent 

 discoveries, essentially modified his account of the function of 

 the rods of Corti, while he included his own later work, 

 which propounded the articulation between malleus and incus 

 as the reason why soft harmonic over-tones arise in the ear itself 

 from the stronger primary tones. The publication of the new 

 edition again led to a few important final observations, which 

 formed his last physiological communication to the Heidelberg 

 Society (June 25, 1869), ' On the Auditory Oscillations in the 

 Cochlea.' This gave fresh support to a hypothesis advanced 

 by Hensen as to the function of the membrana basilaris. 



Helmholtz now turned to his vast undertakings in electro- 

 dynamics. Even if his main work in this direction was to be done 

 a little later, it was in Heidelberg that he began the investiga- 

 tions of which, on Jan. 21, 1870, he presented a part to the Nat. 

 Hist. Med. Ver. with the title ' On the Laws of Inconstant 

 Electrical Currents in Materially Extended Conductors ', which 

 was published at greater length in the same year in the Journal 

 f. reine u. angewandte Math., as 'The Theory of Electro- 

 Dynamics. Part I. On the Equations of Motion of Electricity 

 for Stationary Conductors.' This was a preliminary study to 

 orient himself in the department of hydrodynamics. 



The majority of physicists in Germany deduced the laws of 

 electrodynamics from the hypotheses of W. Weber, which 

 endeavoured to refer the phenomena of electricity and 

 magnetism to a modification of the assumption made by Newton 

 for the force of gravitation, and by Coulomb for statical 

 electricity, of forces acting in a straight line at a distance, 

 their extension through infinite space being regarded as 

 instantaneous, with infinite velocity. Coulomb's view that 

 the intensity of the forces was inversely proportional to the 

 square of the distance of the electrical quantities that exerted 



