ARMY SURGEON AT POTSDAM 35 



confirmation of this law must be the imperative duty of physicists 

 and physiologists. 



The last months of 1846 were wholly taken up with experi- 

 ments on the heat evolved during muscular action. After 

 much discussion with du Bois-Reymond by word of mouth 

 and letter as to the conversion of a thermo-multiplier of 

 extreme sensitivity, by empirical graduation, into a thermo- 

 meter for thousandths of a degree, Helmholtz begs the loan 

 of the portable balance made for du Bois by Halske, 'in 

 order to experiment on the ash of muscle and the composition 

 of nerve with regard to their possible alteration by muscular 

 contraction/ But though du Bois himself brought the balance 

 to Potsdam, Helmholtz was compelled by stress of official 

 duties to break off his experiments for a long time at the 

 end of 1846. The New Year diverted his scientific enter- 

 prises into another and wider field, and was also destined 

 to be the most important of his life in aspects other than 

 scientific. 



After the death of Surgeon-Major von Velten, his widow had 

 moved from Riesenburg to Potsdam with her two daughters, 

 in order to profit by the advantages of the intellectual society 

 to which she was there introduced by her brother (a surgeon- 

 major in the Hussars), and to obtain a good education for her 

 children. Her husband was the son of that Cornet Velten of 

 the Ziethen Hussars, who during the retreat at the battle 

 of Kunersdorf came upon the King, standing alone on an 

 eminence in the field, with his sword driven into the ground 

 in front of him, facing death or captivity. Velten cut his way 

 through, along with Captain von Prittwitz, and helped the King 

 to escape on his own horse, for which he was ennobled, and 

 received the order pour le merite. Frau von Velten was the 

 daughter of the late Hofrath Puhlmann, Court Painter and 

 Director of the Picture-Gallery founded by Frederick the 

 Great. Helmholtz soon obtained an introduction to this dis- 

 tinguished family, though ' at first he was somewhat of a foreign 

 element '. 



His sister-in-law relates that he was ' grave and reserved, a 

 little awkward and shy among other more lively and sociable 

 young men. Some one made the characteristic remark, when 

 Helmholtz was introduced to us, that he was a very clever man 



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