ARMY SURGEON AT POTSDAM 31 



the future soon gave him cause to rejoice over the famous son, 

 by whom the family name was to become known throughout 

 the world. 



Since Helmholtz was entirely thrown upon his own re- 

 sources during these years in Potsdam, the need of scientific 

 intercourse often drew him to Berlin to forgather with his 

 great teacher Johannes Muller, and his devoted friends du 

 Bois-Reymond, Briicke, and Ludwig (who was his senior by 

 five years). The young men were all striking out new paths 

 in their chosen sciences, but they willingly and ungrudgingly 

 gave the palm to Helmholtz, as du Bois-Reymond and Brucke 

 loved to relate in after years. 



Nor was it long before Helmholtz made his mark in a wider 

 circle. Mailer's distinguished pupils at Berlin had become 

 acquainted with other students in physics and chemistry, at 

 the informal classes of their master, Gustav Magnus, and in 

 1845 tne Physical Society had been founded by du Bois-Rey- 

 mond, Brucke, Karsten, Beetz, Heintz, and Knoblauch. Du 

 Bois introduced young Helmholtz to the Society, where he was 

 warmly welcomed as its greatest ornament, and for over ten 

 years contributed reports to the Fortschritte der Physik on 

 certain departments of physics and physiology. 



The riddle of the existence and nature of vital force the 

 question whether the life of organisms was the effect of one 

 special, self-engendered, definitely directed force, or merely the 

 sum of the forces that are effective in inorganic nature also, 

 modified only by the manner of their concurrence such were 

 the questions raised again and again by Muller, and trans- 

 formed by Liebig into the far more concrete problem ot 

 whether the mechanical energy and the heat produced in an 

 organism could result entirely from its own metabolism, or not. 

 Helmholtz soon perceived that all these questions were inti- 

 mately connected with the validity of that law of the Conserva- 

 tion of Energy which had for years seemed incontestable 

 to him; but it was necessary to prove the accuracy of his 

 mathematico-physical propositions by a vast number of experi- 

 ments in different regions of physiology and physics, before he 

 could hope to see the principle admitted by science. He 

 began, therefore, in 1845, by testing the accuracy of his 

 physical conceptions upon a highly complex physiological 



