3 o 4 HERMANN VON HELMHOLTZ 



force the red, and blue light to make it paler, but he further 

 distinguishes greenish rods between the red, which should 

 become more intense with green light. Whether the green 

 is anything more than contrast, still appears to me questionable ; 

 but that other coloured and uncoloured rods lay between the 

 red, I could see for myself from his demonstrations last 

 summer/ 



All this extensive scientific activity did not prevent him, 

 when on the death of Poggendorff in the same year the editing 

 of the Annalen der Physik u. Chemie devolved upon G. Wiede- 

 mann, from giving a helping hand to the editing (as Wiedemann 

 himself informs us), while he contributed a full written report 

 on every paper of mathematico-physical interest that was 

 sent in. 



After his appointment on July 24, 1877, to the Professor- 

 ship of Physics at the 'Medico-Chirurgical-Military-Academy' 

 (Friedrich-Wilhelm Institut), at which he had received his own 

 education, he gave a discourse on * Thought in Medicine ' at the 

 Commemoration Festival of the Foundation of the Institute in 

 the same year, in which he extolled medical studies as the school 

 1 which had demonstrated more clearly and convincingly than 

 would have been possible in any other case, the eternal 

 principles of all scientific work, principles so simple and yet so 

 often forgotten, so clear and yet so often veiled in obscurity '. 

 He points out that medicine more than any other department 

 of science involves insight ; that epistemological questions as 

 to scientific methods might also assume a serious importance, 

 and prove to have a fruitful practical bearing ; that if a man 

 work on a perfectly sure basis he loses nothing by an error save 

 that wherein he has erred, but that where everything rests on 

 hypotheses which only correspond with what we should like to 

 hold true the least rift dislocates the entire structure of our 

 convictions. And then in a most brilliant argument he attacks 

 metaphysical systems in natural science, as well those of the 

 spiritualists, who feel themselves elevated above the rest of 

 nature, as those of the materialists, who strive to control the 

 world unconditionally by means of the conceptual forms they 

 have at present arrived at. 



He shows by a clear and convincing argument that Kant's 

 refutation of the claims of pure thought had defeated the 



