1896.] on Ludwig and Modern Physiology. 19 



before Ludwig's time, investigated the phenomena of life from 

 the physical side, it was he and the contemporaries who were 

 associated with him who first clearly recognised the importance of 

 the principle that vital phenomena can only he understood hy com- 

 jparison with their physical counterparts^ and foresaw that in this 

 principle the future of Physiology was contained as in a nutshell. 

 Feeling strongly the fruitlessness and unscientific character of the 

 doctrines which were then current, they were eager to discover 

 chemical and physical relations in the processes of life. In Ludwig's 

 intellectual character this eagerness expressed his dominant motive. 

 Notwithstanding that his own researches had in many instances 

 proved that there are important functions and processes in the 

 animal organism which have no physical or chemical analogues, he 

 never swerved either from the principle or from the method founded 

 upon it. 



Although Ludwig was strongly influenced by the rapid progress 

 which was being made in scientific discovery at the time that he 

 entered on his career, he derived little from his immediate pre- 

 decessors in his own science. He is sometimes placed among the 

 pupils of the great comparative Anatomist and Physiologist, J. Miiller. 

 This, however, is a manifest mistake, for Ludwig did not visit Berlin 

 until 1847, when Miiller was nearly at the end of his career. At 

 that time he had already published researches of the highest value 

 (those on the Mechanism of the Circulation and on the Physiology of 

 the Kidney), and had set forth the line in w^hich he intended to direct 

 his investigations. The only earlier Physiologist with whose work 

 that of Ludwig can be said to be in real continuity was E. H. Weber, 

 whom he succeeded at Leipzig, and strikingly resembled in his way 

 of working. For Weber, Ludwig expressed his veneration more 

 unreservedly than for any other man excepting perhaps Helmholtz, 

 regarding his researches as the foundation ou which he himself 

 desired to build. Of his colleagues at Marburg he was indebted in 

 the first place to the anatomist. Professor Ludwig Fick, in whose 

 department he began his career as Prosector, and to whom he owed 

 facilities without which he could not have carried out his earlier 

 researches; and in an even higher degree to the great Chemist, 

 R. W. Bunsen, from whom he derived that training in the exact 

 sciences which was to be of such inestimable value to him after- 

 wards. 



There is reason, however, to believe, that, as so often happens, 

 Ludwig's scientific progress was much more influenced by his con- 

 temporaries than by his seniors. In 1847, as we learn on the one 

 hand from du Bois-Reymond, on the other from Ludwig himself, he 

 visited Berlin for the first time. This visit was an important one 

 both for himself and for the future of Science, for he there met 

 three men of his own age, Helmholtz, du Bois-Reymond and Briicke, 

 who were destined to become his life-friends, all of whom attained 

 to the highest distinction, and one of whom is still living. They 



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